Biology: Genetics Unit (+ a bit of miscroscopes)
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97 Terms
What are the magnification of the objective lenses?
4x, 10x, 40x
How do you get total magnification and what are the corresponding values?
Multiply by 10 (ocular lens magnification), 40x, 100x, 400x
What are the FOVs for each objective lens?
4500 um, 1800 um, 450 um
? mm = ? um
1 mm = 1000 um
How do you find the size of a specimen?
size of specimen = FOV / # of specimens seen lengthwise or widthwise
How do you find the drawing magnification?
drawing magnification = measured size of drawing / calculated size of specimen
What is DNA?
molecules that carry the genetic information that directs an organisms function and development
What are chromosomes?
Chromosomes are genetic material that has been condensed into that shape to facilitate mitosis and meiosis
What is a gene?
A segment of a DNA molecule that carries information to produce a specific trait, in a specific location of a chromosome (example: gene determining the trait of eye colour)
What is heredity?
The process by which offspring inherit traits from their parents
What is locus?
A specific location of a gene in a chromosome
What is a nucleotide?
The building blocks that make up DNA; their arrangement codes genetic information
What are the parts of a nucleotide? Be able to label them
A - Deoxyribose
B - Phosphate
C - Nitrogenous base
What are the four bases in nucleotides and how do they pair?
Adenine, Thymine, Cytosine, Guanine
AT and CG
What is the relationship between nitrogenous bases and traits?
The arrangement of nitrogenous bases in DNA codes for genetic material that determines specific traits
What is an allele?
An allele is a variant of a gene, which decides what traits offspring will inherit (example: a specific allele will decide you have blue eyes vs brown eyes)
What are haploid vs diploid cells? Which human cells are diploid or haploid?
Diploid: have two full sets of genetic information (normal number 2n); somatic cells are diploid cells
Haploid: only contain one full set of genetic information (half the normal number = n); gametes are haploid cells
What are somatic cells vs gametes?
Gametes = sex cells
Somatic cells = all other cells
What are the advantages and disadvantages of asexual reproduction?
Advantages: no energy spent on attracting a mate, no danger underwent to do so (mating rituals can result in death by fighting or attracting predators)
Disadvantages: no genetic variation; in case of a changing environment, offspring are less likely to be able to adapt and overcome
What are the advantages and disadvantages of sexual reproduction?
Advantages: genetic variation; offspring are more likely to adapt to a changing environment
Disadvantages: need to have different sexes and mating rituals, can be dangerous to find a mate
What are some natural examples of asexual reproduction?
Budding: outgrowths of body that break off and develop
Runners: new plant grows from roots
Fragmentation: piece breaks off and becomes independent
Describe mitosis
Interphase: normal activities, duplication of genetic material
Prophase: chromatin condenses into chromosomes, nuclear membrane dissolves
Metaphase: chromosomes line up at the equatorial plate, spindle fibers attach to centromeres
Anaphase: spindle fibers pulls sister chromatids apart to sides of cells
Telophase: nuclear memebrane forms around chromosomes, which unravel into chromatin
Cytokinesis: two daughter cells separate (varies between animal and plant cells)
How is cytokinesis different between animal and plant cells?
Animal cells: cleavage furrow forms and cell membrane pinches off
Plant cells: vesicles gather and fuse at the equatorial plate to from a cell plate that turns into a cell wall
How are animals cloned? What are the advantages and disadvantages of this?
Animals are cloned by removing a body cell, fusing it with an egg cell and stimulating the egg cell to grow and differentiate, then placed in a surrogate uterus
Advantages: can control the genetic process, to avoid getting undesirable traits
Disadvantages: cloned specimens suffer from health complications, shorter lifespans, and faster aging
Where does gametogenesis occur in the human body?
Testes in males, ovaries in females
Where does gametogenesis occur in plants?
Flowers and cones
What is spermatogenesis and what are the products?
The process by which 4 sperm cells are produced from one germinal cell through meiosis
What is oogenesis and what are the products?
The process by which 1 egg cell and 3 polar bodies are produced from one germinal cell through meiosis
How many chromosomes does a zygote receive from each parent?
23 chromosomes, for a total of 46
What are homologous pairs? How are they similar and different?
Pairs of chromosomes, one provided by each parent, that are similar in size, shape, and genes present at the same loci locations; what is often different is the alleles present which result in different traits
Explain the process of meiosis
Prophase 1: chromosomes condense, synapsis and crossing over occurs
Metaphase 1: homologous pairs line up
Anaphase 1: homologous pairs are separated
Telophase 1: nuclear membrane reforms
Cytokinesis 1
Prophase 2: chromosomes condense, nuclear membrane dissolves
Metaphase 2: chromosomes line up at the equatorial plate
Anaphase 2: sister chromatids are pulled apart
Telophase 2: nuclear membrane reforms, cytoplasm picnhes off
Which two process in meiosis produce genetic variation? How?
Crossing over: non-sister chromatids in a homologous pair exchange segments, resulting in changes in the information carried and so genetic variation
Random assortment: the random line up of pairs during metaphase 1 ensures many different combination of genes in daughter cells, ensuring variation
Explain how chromosomes are divided so that each gamete has a full set of genetic information
The germinal cell has 46 chromosomes, as it has 23 pairs of homologous chromosomes. During meiosis 1, the homologous pairs will be separated, so that each daughter cells gets one chromosome from each of the 23 pairs. As a result, each daughter cell will have 23 chromosomes. During meiosis 2, the chromosomes will be pulled apart and each daughter cell will have one sister chromatid, which counts as a chromosome. As a result, each of the four daughter cells have 23 chromosomes.
What is reduction division?
The term used to describe meiosis 1, as in this stage cells go from having 46 chromosomes to 23 chromosomes by separating homologous pairs
How can you calculate the number of possible combinations in random assortment?
2^n, n = number of chromosomes in haploid cells
Why is it more beneficial for oogenesis to produce only one ovum with more cytoplasm?
Producing one ovum with more cytoplasm ensures the egg has enough nutrients for when it becomes a zygote, to successfully become an embryo.
Why is it more beneficial for spermatogenesis to produce 4 small sperm cells?
Because sperm cells must be able to move quickly on their own, so less cytoplasm facilitates that
What is a karyotype?
a picture of an individual’s chromosomes that have been sorted and arranged according to size and type
Explain sex determining chromosomes
The 23rd homologous pair determines sex in humans. If a person has XX chromosomes, they are female; if they have XY chromosomes (Y being much smaller), they are male
What is synapsis?
the pairing up of homologous chromosomes during prophase
Who was Gregor Mendel and what did he discover? How?
the “Father of Genetics”
discovered patterns of inheritance (dominant vs recessive traits)
He did this by breeding pea plants and recording what traits the offspring inherited
What were some of the benefits of Mendel’s pea plants? Why was it important they were true-breeding?
The plants were easy to grow, inexpensive, had a short generation time, and were true breeding
It was important that they were true breeding because then there were only two variations per characteristic, making it easier for Mendel to examine how traits were passed down
What is the P generation? What is the F1 generation? What is the F2 generation?
P - parent gen
F1 - filial gen, offspring of P
F2 - offspring of F1
How are dominant and recessive alleles different?
Dominant alleles are always expressed in the phenotype if present, but recessive alleles must be the only allele to be expressed
Define what homozygous and heterozygous means in genetics
Homozygous - the alleles for a gene are the same (HH or hh)
Heterozygous - the alleles for a gene are different (Hh)
Define genotype and phenotype
Genotype: the combination of alleles for any given trait (HH, Hh, hh)
Phenotype: the observable trait that is expressed based on an organism’s genotype (homozygous recessive, heterozygous dominant)
Can you determine the genotype by simply observing an individual, if the trait is dominant?
No, because they could be HH or Hh, but both would express the same trait
What is a Punnett square?
A square diagram that allows one to examine the genotypes of the offspring between two individuals
What is the Law of Segregation? Who came up with it?
Mendel came up with the Law of Segregation, proposing that pairs of alleles are separated during meiosis, so that each gamete gets one copy of each gene; therefore, zygotes get one allele from each parent
How can you determine if an individual is homozygous dominant or heterozygous dominant?
A test cross
The tested individual is crossed with a homozygous recessive individual; if any of the offspring express the recessive trait, the parent is heterozygous dominant
What is incomplete dominance?
When neither allele is dominant, so a blended phenotype is expressed
Example: if the colours of a flower are red and white, the heterozygous trait would be pink. It would be expressed as CRCW
What is codominance?
When both alleles are expressed, and both parental phenotypes are seen in offspring
Example: roan cattle have red AND white hair
How is a female carrier different from a heterozygous female? What are their genotypes?
They are the same thing; their genotypes are the same
How many blood types are there? What are they?
4; A, B, AB, or O
What are the 3 different alleles for blood type?
IA, IB, or i
Paired with i, IA and IB are dominant, but with each other they are codominant
IA IB : AB blood type
IA i: A blood type
IB i: B blood type
ii : O blood type
Why do A and B blood types reject any kinds of blood except their own? What blood type do they not reject?
Because the antigens in A blood are different from the ones in B blood, so if mixed they will reject and clump together; they can receive type O blood because it has no antigens
What blood type is the “universal recipient”? What blood type is the “universal donor”? Why?
Recipient: AB blood type, can receive all blood types
Donor: O blood type, can donate to all blood types because it has no antigens
How is the Rh factor decided?
The positive allele is dominant
What is sex-linked inheritance? Are sex-linked disorders usually dominant or recessive? What are some examples?
Sex-linked inheritance refers to how some genes for certain disorders are located on the X chromosome, instead of the autosomal chromosomes
it is usually recessive
because the allele for the disorder is located on the X chromosome, it is more commonly expressed in men
this is because women have an extra X chromosome, acting as a second chance to get the dominant normal allele, while if men have the recessive allele, they have no other X chromosome to act as a back up
Examples are hemophilia and colorblindness
What is a pedigree? What does it mean when an individual is shaded in?
A chart showing an individual’s ancestors to show patterns of inheritance for a certain trait; also used for selectively breeding animals and plants. If an individual is shaded in, it shows it is affected by the trait being analyzed
What is autosomal inheritance?
inheritance of disorders for which the gene is on autosomal chromosomes
What are some clues on a pedigree chart that a trait is dominant?
All affected individuals have at least one affected parent
Two affected people can have an unaffected child
What are some clues on a pedigree chart that a trait is recessive?
Traits can skip a generation
Two affected parents will only have affected children
What is DNA’s full name?
deoxyribonucleic acid
What are nucleotides and what are the three components of them?
Nucleotides are the building blocks of DNA; the components are nitrogenous base, phosphate, and deoxyribose sugar
What is the role of the nitrogenous base in DNA?
The arrangement of the nitrogenous bases in a specific gene loci determine the genetic information and gene expression of the individual
What was nuclein and who discovered it?
Friedrich Miescher called a compound found in the nucleus, nuclein. This would later be known as DNA
What were Hammerling’s discoveries with the Acetabularia plants?
He discovered that the nucleus was vital to regeneration and other life processes; when the top (no nucleus) was cut off from the rest of the plant, it regrew, but if the foot (has nucleus) was cut off, it did not regrow
How did Hershey and Chase prove that DNA contained hereditary information?
They studied how viruses injected their DNA into bacteria to produce more viruses; however, viruses that only injected a protein into bacteria were not able to hijack the bacteria to produce more viruses
What are the pairings of nitrogenous bases? How can you remember them? Which have two rings?
Adenine and Thymine (A&T) - apple in the tree
Cytosine and Guanine (C&G) - car in the garage
Adenine and guanine have two rings (GiAnt), while thymine and cytosine have one ring (TeenCy)
What are the four nitrogenous bases?
Adenine, Thymine, Guanine, and Cytosine
Who discovered the double helix shape of DNA? How?
Rosalind Franklin, with the help of Maurice Wilkins, by using X-ray crystallography
Who developed the current model for DNA?
Watson and Crick, largely based on Franklin’s research (without crediting her, mind you)
What 3 important things did Watson and Crick’s model show?
DNA has a double helix shape
DNA is made up of phosphate, nitrogenous bases, and deoxyribose sugars
The proportion of A to T is equal, and the proportions of C to G is equal (because they’re paired together?)
What is nondisjunction? What is aneuploidy? What is a trisomy vs monosomy?
Nondisjunction refers to the event of chromosomes not separating correctly during meiosis, resulting in gametes that have extra or missing chromosomes. Aneuploidy refers to the condition of having an extra or missing chromosome (aneuploidic zygotes are the result of nondisjunction). A trisomy is an abnormality where the resulting gamete has three homologous chromosomes instead of a homologous pair. A monosomy is when the gamete has a missing homologous chromosome in a pair.
What is a mutation? What is it caused by? What are the two types?
A change in an individual’s genetic code, having a positive, negative, or neutral impact on the individual
Caused by environmental agents (ex radiation) or errors during cell division
Types: point mutation or chromosomal mutation
What are some common chromosomal disorders + how are they abnormal?
Patau’s: trisomy chromosome 13
Edwards: trisomy chromosome 18
Down’s: trisomy chromosome 21
Turner’s: no Y chrosome, only one X
Klinefelter: three sex chromosomes, XXY
What is point mutation? What are the three types? What is the result of point mutation?
A small-scale mutation occurring through a change in the arrangement of nitrogenous bases in DNA.
Types are base-pair substition (A is switched for T, ex), insertion, and deletion
The result of point mutation is the production of altered proteins
What are chromosome mutations? What causes it?
an error that involves an entire chromosome or a large part of one. It is caused due to nondisjunction occurring during meiosis, producing abnormal gametes
It involves large scale deletions, insertions, or inversions
Which is more dangerous, point mutation or chromosome mutations?
Chromosome mutations, becaue they affect a larger portion of the DNA or the chromosome number
Which can be more dangerous, insertion and deletion or base-pair substitution?
Insertion/deletion, as it will cause the rest of the sequence to be read in the wrong order instead of the usual order of 3s
What kind of mutations are inherited?
Mutations that occur in the gametes are passed down, but those in the somatic cells are not; this is because it is the gametes that form the zygote, causing it to have the mutation in all its cells
How are autosomal recessive and autosomal dominant mutations different?
Dominant: expressed in F1 and every generation after
Recessive: may skip generations and reappear later
What are some examples of mutation disorders? Explain ones like sickle cell anemia and lactose tolerance
Sickle cell: beneficial but also negative; exposes individual to low oxygen levels due to subpar hemoglobin function; also makes carriers and affected resistant to malaria
Lactose tolerance: mutation in chromosome 2 produces an enzyme that breaks down milk
Explain how mutations can be spontaneous or induced.
Spontaneous - occurs through accident, as a result of nondisjunction
Induced - occurs due to exposure to outside factors like UV light, smoking, etc
How can a mutation be beneficial? (Hint: bacteria)
A mutation can be beneficial to an individual because it can cause it to become resistant to outside dangers that can result in injury or death; some examples are sickle cell anemia, which makes affected individuals resistant to malaria, or how bacteria can develop and pass down a gene that makes them resistant to antibiotics
What is a transposon? What is transposition?
A segment of DNA that can move along or between chromosomes
This causes transposition, which is the process of moving a gene sequence from one part of the chromosome to another
What is a microarray?
A kind of genetic testing technology, in which a glass slide is coated in a regular pattern of sample genes. The genetic material being tested is then laid over the microarray chip, and this will point out any mutations that have occurred
What does the term human genome refer to?
The sequence of nitrogenous bases found on the 23 human chromosomes
How much of human DNA is actually coding? What about the other percent?
2% is coding DNA, while the other 98% is considered junk DNA, so mutations are not a concern
What is functional genomics?
the study of the function of specific genes in the human biome
Explain functional genomics with mice
Mice are considered model organisms (organisms with genetic similarity to another) for humans; as a result, scientists use mice to study and understand human genomics
What is DNA fingerprinting? What are some uses?
a technique that creates the banding pattern of DNA, showing the unique sequence an individual has
uses:
prove guilt or innocence
paternity test
determining ancestry
identifying individuals in unmarked graves
prosecute hunters or fishers who hunt or fish certain animals out of season
determine true source of animal
What is a dihybrid cross?
A cross between two individuals for two pairs of alleles (looking at two genes)
What is Mendel’s Law of Independent Assortment?
The alleles of two genes (R and r, Y and y) separate independently during the formation of gametes
Each allele is independent of the other and no two alleles are linked
The alleles are found on different chromosomes, creating four different gametes in different combinations of the alleles
What ratio do you expect in dihybrid crosses?
9:3:3:1
What is continuous variation? What causes it in genetics? List examples of traits
When the phenotypic ratio is not clear cut. It is caused due to additive alleles (when a trait is determine by various genes, so their interaction is additive)
Example: height, body mass
Note 
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