SBI 3U Genetics Unit Review

Interphase

Cell grows, copies its DNA, and synthesizes proteins, prepares for division
- G1, S, and G2 phases,

G1 phase

- stage of interphase in which cell grows

S phase

- synthesis phase of the cell cycle
- stage of interphase were DNA replicates

G2 phase

- last stage of interphase where cell grows and prepares for mitosis

Mitosis (M phase)

- cell's nucleus divides occurs in 5 stages
- Prophase, Metaphase, Anaphase, Telophase
- results in 2 daughter cells same number of chromosomes as parent cell

Chromosome

- structures in a nucleus that contain cell's genetic information

Spindle fibre

- tiny tube-like structures made of protein, chromosomes attach during cell division

Centriole

- cylindrical organelle in animal cells aiding in cell division

Sister Chromatids

- genetic copies of each other ( identical) made during S-phase of interphase
- held together by a centromere

Chromatin

- uncoiled chromosomes in DNA before cell division occurs

Centromere

- region where two sister chromatids are held together

Homologous chromosomes

- pairs of chromosomes that carry the same genes
- made of 4 chromatids (tetrad)

Tetrad

- `a homologous pair formed during prophase of meiosis
- four chromatids

Prophase

- chromatin thickens to form X shaped chromosomes
- each half of X is a copy of original chromosome (chromatid) held together by a centromere
- nucleus disappears, centrioles move to poles, spindle fibers form

Metaphase

- everything moves to the middle
- spindle fibers attach to centromeres of chromatids

Anaphase

- centromeres split apart
- chromatids are split and are pulled to opposite poles of cell

Telophase

- nuclear membrane reappears
- cytoplasm is pinched
- two daughter cells begin to form
- chromatid is now chromatin

Cytokinesis

- division of cells
- separation of cytoplasm
- spindle fibers disappear
- nucleus reappears
- result is 2 daughter cells with same number of chromosomes as parent cell

Meiosis

- process of reproduction division where the # of chromosomes is divided in 2 (diploid to haploid)

Crossing over

- exchange in alleles between homologous chromosomes, producing new allele combinations

Meiosis I

Interphase: G1, S, G2, chromatin replicates into chromatid
Prophase I: centrioles move to poles, tetrad, crossing over
Metaphase I: spindle fibres attach to homologous pairs, tetrads line up at equator
Anaphase I: spindle fibers pull homolgous pairs to poles
Telophase I: nuclear membranes form, cytoplasm pinches
Cytokinesis: 2 new unique cells are formed, DNA from both mom and dad allele in new cells,

Meiosis II

Prophase II: centrioles move to poles, tetrad, crossing over
Metaphase II: spindle fibres attach to homologous pairs, tetrads line up at equator
Anaphase II: spindle fibers pull homolgous pairs to poles
Telophase II: nuclear membranes form, cytoplasm pinches
Cytokinesis: 2 new unique cells are formed
- result is 4 unique cells with 1/4 DNA of parent cell (gamete)

Cell differentiation

- when cells are assigned jobs

Gamete

- haploid reproductive cells
- either sperm or egg
- produced during meiosis

Blastocysts

- developing embryo
- hollow Ball of cells
- a thin walled structure containing cluster of cells that an embryo comes from

Somatic cell

- every cell that just undergoes mitosis
- body cell not reproductive cells
ex: skin cells

Sex cell

- egg or sperm; a sex cell carries half the number of chromosomes found in the other body cells.

Zygote

- fertilized ovum
- diploid cell from 2 haploid cell

Diploid

- cells that carry two copies of every chromosome (2n)

Haploid

- cells that carry half the number of chromosomes (n) as diploids
- gametes, egg or sperm

Spermatogenesis

- process of sperm production
- occurs in testes
- starts with diploid cell: spermatogonium, which grows and then under goes meiosis I and Meiosis II
- the result is 4 haploid sperm cells
- form throughout adult years

Oogenesis

- process of egg production
- occurs in ovaries
- starts with diploid cell: oogonium, which grows and undergoes meiosis I and meiosis II, the cytoplasm doesn't equally divide in meiosis
- the result is 3 polar bodies and 1 egg cell

Bivalent

-the structure formed by the pair of homologous chromosomes during crossing over. Also called a tetrad because it consists of four chromatids.

Sex chromosome

- X or Y chromosome that carry the gene used to determine the sex of a person

Non-disjunction

- error in number
- homologue pairs don't separate properly or sister chromatids don't separate properly

Inversion

- error in structure
- when a segment of DNA is flipped and attaches at the wrong end

Deletion

- error in structure
- when a segment of DNA is deleted

Translocation

- error in structure
- when a segment of DNA breaks off and rejoins in a different spot

Duplication

- error in structure
- a section of a chromosome appears 2+ times in a row

Amnioscentesis

- Prenatal genetic testing
- 14 weeks of pregnancy
- amniotic fluid is taken from amniotic sac and fetal cells are tested to see if there are any genetic abnormalities (Trisomy 21)

CVS (chronic villus sampling)

- Prenatal genetic testing
- 9 weeks of pregnancy
- chorion fetal cell sample is taken

Selective breeding

- process of breeding organisms for desirable traits

Artificial Insemination

- artificial transfer of semen into female reproductive tract

IVF

- In Vitro Fertilization (external)
- eggs and semen are collected
- fertilization occurs in a lab
"Test tube babies"

ET

- embryo transfer (external)
- egg is fertilized outside and implanting it into females uterus

What is PGD?

- Preimplantation Genetic Diagnosis

Ultrasound

- sound waves are sent through the body to get an image of organs or fetus

James Watson and Francis Crick

- determined structure of DNA

DNA

- Deoxyribonucleic Acid
- found in nucleus
- control production of proteins in the cell
- double helix shape
- never leaves nucleus

Gene

- segment of DNA on a chromosome that codes for a specific trait

Nitrogenous base

- Adenine pair w/ Thymine, Cytosine pair w/ Guanine
- Uracil (RNA)

Nucleotide

- repeating unit of sugar (deoxyribose), phosphate and 1 base

Hydrogen bond

- what holds the sides of DNA ladder together

Codon

- specific sequence of 3 adjacent bases on a strand of DNA or RNA that provides genetic code information for a particular amino acid

DNA replication

- DNA copies itself
- semi-conservative: ea. new piece of DNA is made of 1 original strand and 1 new strand
- DNA unzips, original strand grows new strand

RNA

- copy of DNA that leaves nucleus
- ribonucleic acid
- U, A, C, G

Transcription

- unzip one gene in DNA
- match up bases to 1 side of a gene in DNA
- mRNA detaches and moves out and into cytoplasm

mRNA

- message that codes for protein
- moves out of nucleus and into cytoplasm

Translation

- process of making a protein
- mRNA > cytoplasm > attaches to ribosome > tRNA decodes mRNA and bring amino acids to build protein

Amino acid

- 20 different kinds
- building blocks of proteins

Mutation

- error in DNA sequence

Mutagen

- anything that causes change in DNA
ex: x-rays, UV light, nuclear radiation

Trisomy 21

- condition in which an individual has three number 21 chromosomes, resulting in Down syndrome

Genetics

- study of where we get our genes and how

Gregor Mendel

Augustinian monk and botanist whose experiments in breeding garden peas led to his eventual recognition as founder of the science of genetics (1822-1884)

Trait

- topic inherited from parents
ex: hair color, eye color, heighy

Characteristic

- expression of a trait
ex: brown hair, blue eyes)

Genotype

- genetic make-up of an organism
- the 2 alleles inherited from your parents
ex: Dd is a genotype for dimples

Phenotype

- the expression of the genotype
- appearance of a trait in an individual
ex: DD= dimples dd= no dimples

Allele

- alternative form of a gene.

Purebred

- organisms from a distinct type or breed (tall w/ tall and short w/ short)
- share similar traits

Hybrid

- organism heterozygous for a trait
- hybrid cross between 2 different purebred plants (tall w/ short)

Monohybrid cross

- hybrid cross between 2 different purebred plants (tall w/ short)

Filial generation

- offspring of a cross of parent organisms

P1, F1, F2

P1: parent generation, purebred plants
F1: first filial generation, offspring from cross of P1 generation
F2: second filial generation, offspring from cross of F1 generation

Dominant

- trait that is always expressed

Recessive

- trait that is not usually expressed but is still there
- if its homozygous recessive it will be expressed

Homozygous

- having the 2 same alleles for a trait (TT or tt)

Heterozygous

- having 2 different alleles for a particular trait (Tt)

Codominance

- both alleles are dominant and both are expressed ( spotty or checkered feathers)

Incomplete dominance

- blending of two traits
- neither alleles are dominant and a blend of the traits show (red and white genotypes express pink phenotypes)

Multiple allele inheritance

- there are more than 2 alleles for that gene

Multiple gene inheritance

- when a trait is controlled by more than 1 pair of genes

Carrier

- individual who has an unhealthy/recessive allele on 1 part of the chromosome but doesn't express it
- can pass it on to offspring

Law of segregation

- traits are determined by pairs of alleles from each parent
- offspring get one allele from each parent

Law of independent assortment

- separate genes for separate traits are passed independently of one another from parent to offspring

Sex-linked traits

- located on sex chromosomes

Pedigree

- diagram that shows the occurrence of a genetic trait in several generations of a family

Synapsis

- the side by side pairing of homologous maternal and paternal chromosomes at the start of meiosis

Autosome

- Any chromosome that is not a sex chromosome (22 of 23)

X-linked

- gene that is found on the X chromosome
- mothers may be carriers and don't express the trait