Unit 3: Genetics

Amniocentesis

A needle is used to withdraw a sample of amniotic fluid containing fetal cells from the amniotic sac, taken after the 14th week and has a miscarriage risk of 1%.

Allele

Various forms of a gene that occupy the same locus of the chromosome but have different variations.

Anaphase I (Meiosis)

Spindle fibres contract and separate homologous chromosomes, sister chromatids remain attached at the centromere, each pole has a haploid set of chromosomes.

Anaphase II (Meiosis)

Spindle fibres contract and sister chromatids separate, sister chromatids move to opposite poles of the cell.

Autoradiography

An imaging technique that uses radioactive sources contained within the exposed sample.

Autosomes

Chromosomes that do not determine sex and occur in "matching" homologous pairs.

Beneficial Mutations

Mutations that help the survival or an organism.

Centromere

A constricted region of a chromosome, it is the region where the spindle fibres attach.

Chromosomes

Long strands of DNA packaged in condensed, folded structures made up of DNA and proteins, they carry many genes and there are 46 of them in a normal human cell.

Cleavage Furrow

An indentation that appears in a cell's surface when the cell is preparing to divide.

Conjugation

A form of sexual reproduction where bacteria transfer genetic material by fusing together to form offspring.

Crossing Over

Exchange of material between maternal and paternal chromosomes and occurs during late prophase I or early metaphase I.

CVS (Chorionic Villus Sampling)

A tool enters through the vagina and obtains samples of placenta, taken after the 9th week and has a miscarriage risk of 2%.

Diploid

Two chromosomes of each type, referred to as 2n, 46 chromosomes, and basically every other type of cell.

DNA

Hereditary information that must be duplicated so exact copy is passed to daughter cells.

Down Syndrome

The gain of an extra chromosome 21, causes mental disabilities and distinct facial features.

Edward Syndrome

Caused by the gain of an extra chromosome 18 and causes intellectual and physical disabilities.

Equatorial Plate

The middle of the cell.

Error Rate

The frequency of errors in DNA transcription.

Frameshift Mutation

The addition or deletion of a base pair.

Gene

A heritable factor that consists of a length of DNA and influences a specific characteristic; consists of a much shorter length of DNA than a chromosome.

Genetic Recombination

Products have different combinations of alleles.

Genetic Reduction

Produces daughter cells with half the number of chromosomes of the parent cell.

Genetic Variation

The presence of differences in sequences of genes between individual organisms of a species; promoted by fusion of gametes from different parents and is essential for evolution.

Genetics

The study of heredity and the variation of inherited characteristics.

Genome

The entire base sequence of each DNA molecule which also includes mitochondrion and chloroplast DNA.

Haploid

One chromosome of each type, which is 23 chromosomes in humans and commonly referred to as n; only sex cells are this.

Harmful Mutations

Mutations which cause harmful effects, usually because they stop or alter the production of a protein.

Histones

Protein found in DNA that are globular in shape, bind to DNA, and helps give chromosomes their shape.

Homologous Pairs

Two chromosomes that have the same sequence of genes but are not identical because they vary in their alleles; also referred to as tetrads or bivalents.

Human Genome Project

A project that began in 1990 and was completed in 2003 that worked to sequence one set of chromosomes in a human.

Independent Assortment

Creation of gametes that carry different combinations of maternal and paternal chromosomes; occurs during metaphase I.

Interphase (Meiosis, After Telophase I and Cytokinesis)

Centrioles duplicate but there is not DNA replication.

Interphase (Meiosis, Before Prophase I)

Chromatin has replicated resulting in two genetically identical sister chromatids attached at the centromere for each chromosome; 46 chromatids duplicate to 92.

Jacob Syndrome

Caused by a gain of an extra sex chromosomes (XXY) and has no unusual symptoms.

Karyograms

An image of the chromosomes of an organism arranged in homologous pairs of decreasing length.

Karyotype

Property of an organism, an individual's complete set of chromosomes.

Klinefelter Syndrome

Caused by a gain of an extra sex chromosomes (XXY) and causes sexual immaturity.

Laziness (Ignore, Added For Fun)

A trait common to IB students (ignore this please).

Locus

A specific position on one type of chromosome.

Meiosis

A type of cell division in sexually reproducing organisms that reduces the number of chromosomes in gametes.

Meiosis I (Meiosis)

Separated homologous chromosomes results in two haploid cells, n=2.

Metaphase I (Meiosis)

Homologous pairs/tetrads/bivalents line up at the equatorial plate, spindle fibres attach to the centromere of each chromosome (one spindle fibre), crossing over can occur.

Metaphase II (Meiosis)

Spindle fibres attach to centromeres of sister chromatids, sister chromatids line up along the equatorial plate.

Monosomy

The loss of a chromosome.

Mutagen

An agent that causes a change in the DNA of a cell.

Mutation (Genes)

Spelling mistakes in the DNA that cause new alleles to be formed by the other alleles; most are neutral or harmful but it can also be beneficial.

Nondisjunction

This occurs when homologous pairs or sister chromatids do not separate as they should in meiosis and can occur in anaphase I or II; risk of this is influenced by maternal parent's age.

Patau Syndrome

Caused by the gain of an extra chromosome 13 and causes intellectual and physical disabilities.

Pilus

A long protein bridge in which two cells join together.

Point Mutation

A single nucleotide base change of the DNA.

Prophase I (Meiosis)

Nuclear membrane breaks down, DNA condenses into chromosomes (each with two sister chromatids), crossing over occurs, and centrioles move to opposite poles.

Prophase II (Meiosis)

Nuclear membrane breaks down, sister chromatids condense, centrioles move to opposite poles and sprout spindle fibres.

Sex Chromosomes

The pair of chromosomes that determine sex.

Sex Determination

Two chromosomes in humans that determine sex, X and Y; SRY or TDF genes found on the Y chromosome tells you if you are a biological male; fetuses with two X chromosomes do not have this gene.

Sexual Reproduction

The process in which haploid sperm and egg cells fuse together to produce a diploid zygote in a process called fertilization.

Sickle Cell Anemia

A co-dominant genetic disease caused by a point mutation in the gene that codes for alpha-globin polypeptide in hemoglobin where the transcription of the 6th amino acid results in valine instead of glutamic acid causing low O2 concentration and a sickle shape.

Silent Mutations

Mutations that do not change the amino acid sequence nor the final protein.

Spindle Fibres/Microtubules

Extends from the centrioles in cell division and attaches to chromosomes.

Telophase I and Cytokinesis

Nuclear membrane reforms, sister chromatids unwind to form chromatin, foundation of cleavage furrow and division of cytoplasm, results on two haploid cells.

Telophase II and Cytokinesis (Meiosis)

Chromatids reach opposite poles, nuclear envelope forms, foundation of cleavage furrow and division of cytoplasm, results in four haploid cells.

Triple X Syndrome

Caused by a gain of an extra sex chromosomes (XXX) and causes tallness, thinness, and menstrual irregularity.

Trisomy

The gain if an extra chromosome.

Turner Syndrome

Caused by the loss of a sex chromosome (XO) and causes a short, webbed neck and sexual underdevelopment.

A Vertical Line With Two Diagonal Lines (Pedigree)

Represents identical twins.

Autosomal Dominant Pattern of Inheritance (Pedigree)

Occurs when the disease -causing allele is dominant; usually every generation has an affected individual and unaffected parents cannot have an affected child.

Autosomal Recessive Pattern of Inheritance (Pedigree)

Occurs when the disease-causing allele is recessive and two unaffected parents can have an affected child if they are carriers; can skip generations.

Benefits of Genetically Modified Organisms (GMOs)

Can add nutritional value to foods, can be produced with lack of known allergens, has better yield as it can be grown in harsher conditions, can produce herbicide, can improve food supply, has longer shelf lives, and reduces economic costs and carbon footprint.

Blunt Ends

The end of a DNA fragment resulting from the breaking of DNA molecule in which there are no unpaired bases, hence, both strands are of the same length.

Budding

In which cells split off the parent organism, generating a smaller daughter organism which eventually separates from the parent; occurs in hydra.

Carrier

A person who has the capability of passing disease to their children even if they do not have the disease themselves.

Causes of Mutations

Radiation from things such as gamma rays, radioactive isotopes, UV rays,and ultraviolet; some chemicals such as those in tobacco, chemical gas, and BPA.

Cloning

In which an organism produces a genetically identical copy of itself.

Cloning Adult Animals

In which a donor cell is taken from an adult animal, an egg is taken from another, the nucleus and egg are fused using an electric shock, the fused cell begins dividing normally and the embryo is placed in the uterus f a foster mother to be fertilized.

Cloning Animal Embryos

Easier to clones as it is pluripotent and could possibility divide into two or more identical part; is more rarely done as it is not possible to assess whether the individual has desirable traits.

Codominance

The condition in which both alleles for a trait are equally expressed in a heterozygote and therefore, both alleles are dominant.

Cystic Fibrosis

A recessive disease caused by DNA deletion of the CFTR gene on chromosome 7; causes mucus to be more viscous and block the lungs and airways and difficulty breathing; diagnosed by analyzing if there is a high salt level, and genetic tests; treated by an altered diet, antibiotics, lung infection, and chest drain.

Diagonal Line Struck Through a Shape (Pedigree)

Represents a deceased person.

Diamond (Pedigree)

Represents a person whose sex is not known.

DNA Ladder

A sample of known length and sequence.

DNA Ligase

An enzyme that joins DNA molecules together by forming the sugar-phosphate bonds between nucleotides used to seal nicks formed by sticky ends.

DNA Profiling

Where DNA from an individual or a crime scene is obtained and used to identify a suspect; used in crime scenes and sometimes paternity cases.

Dolly the Sheep

The first cloned mammal who was cloned in 1996 after 277 attempts.

Dominant Allele

Represented by an uppercase letter, these genes essentially overpower the when only one is present.

Dominant Genetic Diseases

A disease in which one only has to have one copy of the gene to be affected and there are no carriers.

Doubled Horizontal Line (Pedigree)

Represents a consanguineous marriage/mating/children birthing.

F0

Known as the parent generation.

F1

The first generation of offspring produced by parents.

F2

The second generation of offspring.

Factors That Affect Rooting of Stem Cuttings

The cutting piston, the length of the cutting. the growth medium, the temperature, the availability of water, and environmental conditions such as the pH of soil and light exposure.

Gel Electrophoresis

Used to separate proteins or fragments of DNA in an electric field according to charge and size.

Genetic Modification

The transfer of genes from one species to another due to the genetic code being universal.

Genotype

The combination of alleles for any given trait.

Germline Mutations

Occurs in egg or sperm and can be inherited, can cause family cancer syndrome.

Gregor Mendel

This weird monk dude who had an obsession with pea plants, studied botany and mathematics, and is said to be the father of modern genetics.

Hemophilia

An X-linked recessive disease in which the blood does not clot properly and bleeding continues for much longer.

Heterozygous

An individual with two different alleles of a gene.

Homozygous

An individual with two identical alleles of a gene.

Horizontal Line (Pedigree)

Represents mating/marriage/children making.

Huntington's Disease

A dominant disease caused by too many CAG repeats on the HTT gene of chromosome four; symptoms typically start between 30-50 years old and causes the deterioration of the brain; diagnoses by genetic testing, reviewing family medical history, and an examination; is incurable.