TTU BIOL 3810 - Final Exam (Exam 4) General Genetics; Carla Hurt; Fall 2019

Blending Theory

population tends to move towards average (phenotypically)

George Mendel

Crossed peas, Mendelian inheritance. Father of genetics.

Genetics

Studies of all aspects of genes

Gene

fundamental unit of bio. inheritance

Genome

one copy of an organisms complete set of DNA

Genomics

the study of genomes

DNA

deoxyribonucleic acid

Boveri and Sutton

Discovered Chromesome

Watson and Crick

Molecular structure of DNA

Nitrogenous bases (4)

Adenine, Thymine, Cytosine, Guanine

DNA Structure

1) Sugar

2) Phosphate backbone

3) Nitrogenous Base

Bonds between Nucleotides?

Phosphodiester

Homolog

One from each parents, usually carry same genes, different alleles

Intron

non-coding region of DNA

exons

coding region of DNA

Nucleosome

8 histones wrapped in DNA (146bp DNA) (H1 is a stabilizer)

Centromere

constriction where sister chromatids of a chromosome are held together

Telomere

End of Chromeosome

Telomerase

adds length to telomeres

Heterochromatin

transcriptionally inactive

Euchromatin

transcriptionally active

Mitochondrial DNA

Females inherited, Eukaryotic

Chloropalst DNA

organelle inherited DNA in plants

Three types of Protein

structural, enzymatic, regulatory

Transcrption

DNA to RNA

Codon

combination of 3 nucleotides

Mutations

Main source of genetic variation

molecular phylogenetics

changes at the level of DNA used to reconstruct evolutionary history of evolution

Organisms good for genetic research

small, easily reproduce in lab short life span

True breeding variety

pure line, inbred

Backcross

Cross b/t hybrid and parent lines

Forward genetics

Start with random single-gene mutant, and with its DNA sequence and biological function

Reverse Genetics

Start with genomic analysis to determine genes, induce mutations to see affect on phenotype

first law of segregation

In the formation of gametes, members of a gene pair separate into egg and sperm

Interphase

Replication of sister chromatids

tetrad/bivalent

homologous pairs come together for cross-over

prophase 1

Chromosomes condense

synapsis

Prophase 1, cross-over occurs here

Metaphase 1

Bivalents move to center

Anaphase 1

Bivalents randomly seperate

law of independent assortment

the law that states that genes separate independently of one another in meiosis

Telophase 1

Separation of daughter cells

Prophase 2

Dyads recondense

Metaphase 2

Dyads go to middle of cell

Anaphase 2

Dyads separate into monads

Telophase 2

Division and formation of nuclear envelope. Haploid daughter cells

Null mutation

complete loss of function

Leaky mutation

reduced function

silent mutation

no perceptible change

haplosufficient

A gene can function with one copy (like when the other is mutated) (opposite: haploinsuffcient)

Autosomal Recessive

rare, skips generations

X-recessive

usually only in males

X-dominat

males pass to all daughters, no sons

Y-linked

father passes to all sons

Chi-squared test

Sum: (O-E)^2/E, DoF = n-1

Two sources of recombination

Cross-over, independent assortment

inbreeding depression

reduced fitness

polygenic tratis

Trait that has multiple genes controlling it

cytoplasmic segregation

process by which cytoplasmic DNA randomly separates into daughter cells

Gene mapping

allows us to link genes with their function

recombination mapping

mapping of linkage groups with one map unit representing 1% recombination

Parentals

two equally occurring, >50% in recombination mapping

Chiasmata

actual crosses of crossed over DNA during prophase 1

% recombinace

sum of recombinants for two respective alleles divided by total number of progeny. This is the distance between to alleles.

dominant negative mutation

A non-dominant mutation interferes with the dominant gene, so the mutation appears dominant but it really just interfering with the dominance.

Incomplete Dominace

each wild type produces one 'dose' of a protein, dosage determines phenotype (e.g. white and red flower make a pink flower)

Codominance

each wild type allele is represented equally (e.g. white and red flower make a spotted white and red flower)

recessive lethal

kills an organism when exposed

Pleiotropy

The ability of a single gene to have multiple effects on phenotype

antagonistic pleiotropy

one gene has both beneficial and negative effects (e.g. sickle cell disease and malaria)

Synthetic Pathway

A chain of enzymatic reactions (e.g. PKU)

signal transduction pathway

The process by which a signal on a cell's surface is converted into a specific cellular response.

Developmental pathway

(e.g.) Zygote to Adult

Steps for Detecting Gene Interaction

1) Test Cross

2) Test For Allelism (complementation)

3) Combine mutants in pairs to see if genes interact

(2) Test for Complmentation

1) Cross two individuals that are homozygous for two different recessive mutations

2) See if progeny are wild type

3) WT: Then the alleles are complementary (that is, they are on different genes)

4) If nto wt, then they are allelic, on the same gene.

9:3:3:1

no interaction

9:7

Shared pathway

9:3:4

recessive epistasis

12:3:1

dominant epistasis

Epistasis

A type of gene interaction in which one gene alters the phenotypic effects of another gene that is independently inherited.

Penetrance

The percentage of individuals with a particular genotype that actually displays the phenotype associated with the genotype.

incomplete penetrance

Not all individuals with a mutant genotype show the mutant phenotype

Expressivity

the degree to which a trait is expressed (i.e. the intensity)

supressor mutation

suppresses the effect of an earlier mutation at a different site

modifier genes

enhance or dilute the effects of other genes

synthetic lethal

refers to a double mutant that is lethal, whereas the component single mutations are not

abberant euploidy

more or less the normal ploidy level

Euploidy

the correct number of chromosomes in a species

monoploid

of a cell or organism having a single set of chromosomes (but is supposed to be diploid (different from haploid))

Polyploidy

Higher levels of ploidy. Even numbers are favored

Autopolyploidy

an individual that has more than two chromosome sets that are all derived from a single species

allopolyploidy

an individual that has more than two chromosome sets that are all derived from multiple species

Triploids

Typically autotriploid. Sterile due to unpaired chromosomes in Meiosis 1

Colchicine

induces polyploidy (can be used to make haploid plants into diploids by farmers)

Aneuploidy

Abnormal number of chromosomes. (typically 2n +/- 1)

parthenogenesis

Asexual reproduction in which females produce offspring from unfertilized eggs.

trisomic

2n+1

Nondisjunction

the failure of one or more pairs of homologous chromosomes or sister chromatids to separate normally during nuclear division, usually resulting in an abnormal distribution of chromosomes in the daughter nuclei.

Monosomy

2n-1, usually deleterious due to unmasked recessive lethals

Turner Syndrome

monosomy XO