Introduction to Genes (copy)

DNA

the genetic material in a cell

Chromosome (what is it made of, two kinds of chromosome, chromosomes in humans?)

* Made up of **condensed packed** __**chromatin**__
* chromatin made up of __**DNA and Protein**__
* Single-stranded chromosomes (made of one chromatid) and double-stranded chromosomes (made of __two sister chromatids__ and a __centromere__)
* Ex. In **mitosis**, there are 46 single-stranded chromosomes (__46 chromosomes, 46 chromatids__). In **interphase,** they are duplicated becoming 46 double-stranded chromosomes (__still 46 chromosomes, but 92 chromatids__)
* humans have 46 chromosomes (23 pairs, one set from each parent)
* “a condensed unit of DNA”

gene

* portion of DNA (section of a double helix)
* part of a chromosome that contains the information for a trait/protein

allele

* an alternate form of a gene
* two alleles can have the same gene but have different forms/outputs (can both make up the eye colour trait, but one outputs blue and the other outputs brown)
* two alleles (one from parent, one from the other parent) make up a gene in DNA (a portion of the DNA double helix)
* The two alleles (forms of a gene) from the parents come together and determine if the offspring will inherit one form of the gene (ex. can taste ptc) or the other form of the gene (ex. cannot taste ptc)

Protein

* large macromolecules with many functions in living organisms
* Proteins made by instructions from DNA


* made up of many building blocks of amino acids
* proteins from different genes determine traits

Amino Acids

* small molecules that are linked together to form proteins
* amino acids make a protein based on their sequence

Karyotype

* Photo of all pairs of chromosomes in a single cell
* chromosomes ordered via biggest to smallest, last pair being sex chromosomes (X and/or Y)
* Chromosomes are **double-stranded** when karyotypes are taken
* Because it is taken during or right before __**metaphase**__ (not __anaphase__ or __telophase__ because the double-stranded chromosomes are split into single-stranded chromosomes (chromatids) at that point)
* Also not taken during __prophase__ and __interphase__ because the DNA are chromatin (not condensed chromosomes)

Homologous Chromosomes

* chromosomes that have the same shape and size, allele pattern, and centromere position
* In a karyotype the two pairs under the number are actually __**two double stranded homologous chromsomes.**__

Autosomal Chromosomes

all chromosomes that do not determine sex of cell (in karyotype, cells 1-22)

Sex Chromosome

* an X or Y chromosome that determines the genetic sex of an organism
* **NOT** homologous chromosomes
* ex. XY, male (organism will be sperm-producing and develop testes)
* ex. XX, female (organism will be egg-producing)

Diploid

* A cell that contains 46 chromosomes (two sets of 23)

Haploid

* cells that contain one set of chromosomes (23, half of 46)
* sperm cells and egg cells

gametes

* sex cells for any organism
* In humans, sperm and egg
* in plants, pollen

Fertilization

The joining of male and female gametes

Zygote

a diploid cell formed by the fusion of two gametes

* Ex. humans, combination of sperm and egg (23 + 23 = 46)

Explain each part of this double stranded chromosome (except 3 and 4)

1) Chromatid: a single strand of a double stranded chromosome

2) centromere: region where two sister chromatids are joined to form a double-stranded chromosome

**sister chromatids:** one of the two strands of chromosome that are genetically identical

entire thing is a **chromosome**

Double helix (and its strucuture)

* two strands of DNA going in opposite directions
* each strand has nucleotides running through and are connected via bases (which are connected by hydrogen bonds)

Nucleotide

* basic building block of RNA and DNA (nucleic acids)
* made up of three parts:
* phosphate group
* sugar (deoxyribose)
* nitrogenous base

4 bases in DNA

A, T, C, G

Adenine, Thymine, Cytosine, Guanine

* Note: DNA is the sequences of these bases

Complimentary Bases (describe and give the two pairings)

Bases that always pair up with each other

A and T (apple tree)

G and C (car garage)

How do DNA double helix vary among species

* amount of bases
* sequences of bases

How many hydrogen bonds connect the two base pairings?

A and T: 2

C and G: 3

RNA vs DNA

* RNA similar to DNA, but single stranded compared to DNA’s double stranded

Protein synthesis

* process of making proteins
* two stages: **transcription, translation**
* Transcription: RNA gets instructions from DNA
* Translation: RNA makes proteins based off instructions

somatic cell

any of the body cells except the gametes (sex cells)

compare cells involved

Mitosis somatic cells Meiosis gametes (reproductive cells)spermatogoniaoogonia

compare \# of chromosomes in parent cell

Mitosis diploid Meiosis diploid

compare \# of cell divisions

Mitosis 1 Meiosis 2

compare \# of chromosome duplications

Mitosis 1 Meiosis 1

compare \# of daughter cells

Mitosis 2 Meiosis 4

compare \# of chromosomes in daughter cells

Mitosis diploid (humans 46) Meiosis haploid (humans 23)

compare daughter cells to their parent cell

Mitosis genetically the same to parent cell Meiosis genetically unique to parent cell

compare function of the process

Mitosis replication/duplicationgrowthrepair Meiosis formation of gametesreduction of chromosomes

compare role of resulting cells

Mitosis somatic cell (growth and repair) Meiosis reproduction (gametes, sperm cells, egg cells)

name the two processes that provide genetic variation

crossing over and independent assortment

explain survivability of gametes with errors

tend to die, some stay alive

what happens to the cells of a gamete that is fertilized into a zygote

all cells will contain the abnormality because they are produced by the zygote

what are the two types of chromosomal errors?

changes in chromosome structurechanges in chromosome numbers

during \___, what happens to the chemical bonds that hold the DNA in chromosomes together?

during crossing over, the bonds are broken and reformed. Sometimes they do not reform correctly

name the four errors in chromosome structure

deletion, duplication, inversion, translocation

explain deletion and give example

piece of chromosome deletedEx. Cri du Chat syndrom

explain duplication and give example

section of chromosome appears two or more times in a rowEx. Charcot-Marie-Tooth Disease

explain inversion and give example

section of chromosome is invertedEx. FG Syndrome

explain translocation and give example

segment of one chromosome becomes attached to a different chromosomeEx. Chronic Myelogenous Leukemia

define non-disjunction

when homologous chromosomes or sister chromatids do not separate during meiosis

when can non-disjunction occur? describe what happens in each event

anaphase 1 or 2 of meiosisAnaphase 1: homologous pairs do not separate to opposite poles. Instead, one entire homologous pair is pulled to the same poleAnaphase 2: sister chromatids do not separate to opposite poles. Instead, both sister chromatids are pulled to the same pole

what is the end result of non-disjunction?

gametes with too little or too many chromosomes are produced

explain the chances of non-disjunction as maternal age increases

as maternal age increases, chances of non-disjunction also increase

define monosomy

the loss of a chromosome due to non-disjunction

define trisomy

the gain of an extra chromosome due to non-disjunction

What is prenatal Genetic Testing?

tests performed on a fetus to look for genetic abnormalities

what is amniocentesis?

a common invasive testamniotic fluid surrounds the fetus; needle inserted to withdraw a sample of the fluidfluid contains DNA of fetusmonitors chromosome abnormalities, genetic disorders, and malformations of the spine and brain

what are chorionic villus sampling? (CVS)

a common invasive testA chorion collects DNA from fetus (placental tissue)monitors chromosome abnormalities, genetic disorders, and malformations of the spine and brain

are there genes that contain multiple alleles? where does this inheritance occur?

yes there are genes that contain multiple allelesThis inheritance is found in human blood

For human blood type, what alleles are there? How many of the three alleles do humans have? what are the four blood types?

A, B, OHumans have 2 of three allelesthe four blood types are A, B, O, AB

describe what the red blood cells for a person with Type A blood looks like

red blood cells have A antigens (round things) on their surface

describe what the red blood cells for a person with Type B blood looks like

red blood cells have B antigens (spiky things) on their surface

describe what the red blood cells for a person with Type O blood looks like

red blood cells have no antigens (nothing) on their surface

describe what the red blood cells for a person with Type AB blood looks like

red blood cells have both A and B antigens (round and spiky things) on their surface

what is the universal allele for type A blood?

I^A (uppercase I)

what is the universal allele for type B blood

I^B (uppercase I)

what is the universal allele for type O blood

i (lowercase i)

What is the universal allele for type AB blood?

I^A I^B (uppercase Is)

explain the relationship between the blood type alleles

Alleles I^A and I^B are codominant and are both dominant to i (blood type O)homozygous recessive individuals have blood type OFor heterozygous individuals with I^A i, they have blood type AFor heterozygous individuals with I^B i, they have blood type B

Explain progressive dominance

a type of multiple allelesa group of alleles that is in order based on dominanceTherefore, each allele is dominant to the alleles that follow itC \>  c^ch   \>  c^h   \>   cProgressive dominance is written this way, with the \> representing dominant to

describe blood composition

mostly plasmasolid portions made of white blood cells and red blood cells

what do red blood cells contain?

antigens (proteins)

what does blood plasma contain?

seperate molecules called antibodies

what are antibodies? what does it do?

proteins used in immune system to protect youwhen an antibody matches a blood cell antigen, it will cause agglutinationEx. Blood type A has a antigens and antibody-B. if person receives blood type B, their antibody-B and the blood type B will clump together

BLOOD TYPE A describe antigens (and their shape), antibodies, safe and not safe donors

BLOOD TYPE B describe antigens (and their shape), antibodies, safe and not safe donors

BLOOD TYPE AB describe antigens (and their shape), antibodies, safe and not safe donors

BLOOD TYPE O describe antigens (and their shape), antibodies, safe and not safe donors

what is a universal receiver?

someone who is blood type AB+ because they can receive blood from all donorsCan receive blood from A, B, AB, OCan receive blood from - and +

what is a universal donor? why is it a universal donor

Someone with blood type O- because their blood can be given to any blood typecannot be blood type O+ because not everyone can accept positive blood (ex. Rh - like O-, AB-, B-, A-)Anyone can receive - (both Rh + and Rh -)

What are the two types of Rh

positive and negative

explain Rh Positive

has Rh antigenshas no Rh antibodiescan receive both + and - blood

explain Rh negative

has Rh antibodieshas no Rh antigenscan only receive - blood

(to practice terminology) A woman with blood type A needs a blood transfusion.  Can she receive type AB blood?  Explain why or why not?

She cannot receive type AB blood because she has antibody B which will agglutinate with the antigen B on the Donor’s blood

Define Hemophilia (compare how it affects men vs women)

Recessive inherited genetic disorderimpairs body’s ability to control blood clotting/coagulation (used to stop bleeding when a blood vessel is broken)Affects people with XY sex chromosomes (biological male) much more than people with XX

Explain why hemophilia affects men more than women

gene that controls blood clotting is on x chromosomeswomen have 2 X chromosomes while men have 1

Define Sex-linked traits (and how it affects women)

Tendency for certain inherited characteristics to occur far more frequently in one sex than anotherGenes for the traits found on sex chromosomes (X or Y)For a person with XX sex chromosomes to be affected by sex-linked recessive trait:Must have both recessive alleles (ask ms dean to explain)

How do sex linked traits affect men?

Sex linked traits can be carried on the Y chromosomeTherefore, only men (XY, biological males) can be affected

How do you represent crossing individuals with sex-linked traits?

x-linked dominant trait: X^Ax-linked recessive trait: X^a There could also be codominant/incomplete dominance situation with the sex-linked traits (X^O, X^B, X^O X^B)

what is a carrier? What is their genotype? Explain how it affects her

A biological female who is heterozygous for a sex-linked traitX^a, X^a would NOT be considered a carriergenotype: X^A, X^aNot affected by the recessive trait even though she is carrying it because the dominant trait is protecting hercan still pass the recessive trait on to her children

when you see “sex-linked” in a question, which sex-linked do you assume?

assume X-LINKED unless stated otherwise

define true breeding plants

organisms that exhibit same traits each generationwas named the parental generation (P)

Explain the Principle of Dominance (based on Mendel’s experiment of crossing yellow and green peas)

Mendel conluded that there were two hereditary factors for each trait he studiedCalled alleles today (different forms of a gene, diploids have 2 alleles per gene)Determined that yellow was the dominant alleleForm of a trait that always appears on the offspring when an individual has an allele for itDisplayed using uppercase letter (A)Determined that green was the recessive alleleform of a trait that only appears when an individual has two alleles for itDisplayed using lowercase letter (a)Example: AA \= yellow, Aa \= yellow, aa \= Green

explain law of segregation

traits are determined by pairs of alleles that segregate during meiosis so that each gamete receives one allele

Define Genotype

the combination of alleles for any given traitwhat two alleles do they have? to give them their final traitEx. AA, Aa, aa

Define Phenotype

the physical and physiological traits of an organismWhat do you see physically? What is it doing?Eg. Colours yellow or green

define homozygous

organism that has two identical alleles of a geneEg. AA, aa

define heterozygous

organism that has two different alleles of a geneEg. Aa

Define Incomplete Dominance

heterozygotes show an intermediate phenotype (mix/blend of alleles)neither allele is completely dominant

Define Codominance

heterozygotes show both phenotypes (two separate sections of each allele)both alleles are dominant

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what is meiosis? what are the key outcomes?

production of gametes (sex cells) with a haploid (23 chromosomes) number of chromosmestwo key outcomesgenetic reduction (creates haploid cells 46 → 23)genetic recombination (creating diversity)

What are the stages of entire meiosis

meiosis 1 prophase 1 metaphase 1 anaphase 1 telophase 1 meiosis 2 prophase 2 metapahse 2 anaphase 2 telophase 2

explain prophase 1

process called Synapsis\** occursaligning of homologous chromosomesof chromosomes in cell is diploidNuclear membrane/nucleolus disappearcentrioles move to polesspindle fibres formCrossing Over\** occurs