Genetics Unit 1 Exam

Transmission genetics

Hereditary and how traits are passed from generation to generation

Molecular genetics

Chemical nature of the gene

Population genetics

Genetic composition of groups of individuals

Monohybrid cross ratio

3:1

Testcross

A cross between an organism of unknown dominant genotype with an organism of known recessive genotype

Why did Mendel use pea plants?

1. Many varieties
2. Easy to cross
3. They could self fertilize

Monohybrid cross supports:

Segregation

Dihybrid cross supports:

Independent assortment

Dihybrid cross ratios

9:3:3:1

Trihybrid cross ratios

27:9:9:9:3:3:3:1

Chromosome

a threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes.

Interphase

Period of cell cycle for cell growth

S phase

DNA synthesis

Prophase

Condensation of chromosomes. Spindle apparatus forms

Prometaphase

Spindle fibers interact with sister chromatids. They connect to the kinetochore

Metaphase

Chromosomes line up in the middle of the cell

Anaphase

Centromeres divide longitudinally (sister chromatids are then considered chromosomes)

Telophase

Nuclear envelope forms around each group of chromosomes

Meiosis results in

4 haploid daughter cells

Leptotene

Chromosomes become visible as long, threadlike structure; pairing of chromosomes; double strand breaks (lepto- "thin like") (1)

Zygotene

Synapsis of homologous chromosomes begins; synaptonemal complex begins to form (2)

Pachytene

Complete formation of synaptonemal complex and crossing-over begins (pachy- "thick") (3)

Diplotene

synaptonemal complex disappears, chiasma still present (diplo- "two") (4)

Diakinesis

Maximum chromosome contraction

Mitotic spindle

An assemblage of microtubules and associated proteins that is involved in the movements of chromosomes during mitosis.

Epigenetics

The study of environmental influences on gene expression that occur without a DNA change

Incomplete dominance

Intermediate heterozygote phenotype

Codominance

Heterozygote shows phenotype of both parents

Complementation

Phenomenon in which two parents that express the same or similar recessive phenotypes produce offspring with a wild-type phenotype.

Two albino parents have 4 normal offspring. This is an example of:

Complementation

3 ways dominant mutant alleles can affect phenotypes:

Gain of function, dominant-negative mutation, and haploinsufficiency

Germline mosaicism

Specialized type of mosaicism where some gametes carry the mutation and rest are normal
May produce a disease in the offspring that is not carried by parent's somatic cells
AND/OR cause only some offsprings to be affected by autosomal dominant, completely penetrant disease

One map unit is equivalent to:

1% recombination frequency

Probability of a double crossover:

the product of the probabilities of the single crossovers (times the total to get expected number)

Interference

1 - c where c is observed crossovers/expected number

Dosage compensation

Theory that X chromosome inactivation equalizes gene expression between males and females

Barr body

A dense body formed from a deactivated X chromosome

Sex limited

When expression of a gene depends on the sex of the individual.

Mitochondrial inheritance

Disease occurs in both males and females, inherited through females only

Homoplasmy vs heteroplasmy

Mitochondria within a cell can all have the same mtDNA (homoplasmy) or 2 or more mitochondrial genomes (heteroplasmy)

Mutational load

% of mitochondria that are mutant correlates with the degree of biochemical deficiency