Genetics exam

Central dogma theory

B

Mechanical structure of DNA

B (double helix)

Define Genetic transcription

Transcription produces RNA

Difference between plant and animal cells

Plant cells:have cell walls and chloroplasts

animals cells: don’t

Simple Mendelian segregation ratios

Monohybrid Cross (one trait) Aa × Aa 3:1

Test Cross Aa × aa 1:1

Dihybrid Cross (two traits) AaBb × AaBb 3:1

Segregation ratio of a dihybrid cross

9:3 3:1

relationship between genome and chromosomes

chromosomes make up a genome

characteristics of a chromosome

• Made of DNA + proteins (histones)

• Contains many genes

• Has a centromere (attachment point)

• Can be replicated → forms sister chromatids

• Found in the nucleus (in eukaryotes)

• Number is species-specific (e.g., humans have 46)

Ploidy numbers

n = 1 set
2n = 2 sets
>2n = multiple sets

Definition of a locus on a chromosome

The specific location of a gene on a chromosome

Difference between a heterochroatin and a euchromatin

Heterochromatin: tightly packed, inactive DNA

Euchromatin: loosely packed, active DNA

difference between meiosis and mitosis 2x

Mitosis: 1 division → 2 identical diploid cells

Meiosis: 2 divisions → 4 different haploid cells

phases of mitosis

Prophase

Metaphase

Anaphase

Telophase

What happens in mitotic prophase

Chromosomes condense

Nuclear membrane breaks down

Spindle fibers form

Difference between coupleing and repulsion

Coupling (cis): dominant alleles on the same chromosome

Repulsion (trans): dominant alleles on different chromosomes

difference between exon and intron

Exon: coding DNA, expressed in protein

Intron: non-coding DNA, removed during RNA splicing

What is a chiasmata?

points where homologous chromosomes exchange genetic material during meiosis, contributing to genetic variation

Additive gene action

Multiple genes add together their effects to determine a trait (no single dominant gene)

Epistatic gene action

One gene masks or modifies the effect of another gene

dominant gene action

One allele completely masks the other in a heterozygote

Overdominant gene action

The heterozygote is more extreme or superior than either homozygote

Narrow-sense heritability

The proportion of trait variation due to additive genetic effects (predictable inheritance).

reduction of heterozygosity during self-pollination

decreases by ~50% each generation as alleles become homozygous

Value/consequence of an experiment having more replication

It reduces random error and makes results more reliable and accurate

What goes in the denominator when calculating broad sense heritability

VP

Transgressive segregation

Offspring show traits beyond the range of both parents due to new allele combinations

PCR

Polymerase Chain Reaction — a method to amplify (make many copies of) DNA

SNP

Single Nucleotide Polymorphism — a one-base DNA difference between individuals

Co-dominant markers

Markers where both alleles are visible in the heterozygote (you can tell AA, Aa, and aa apart)

Hardy Weinberg Equilibrium

1=p²+2pq+q²

Genetic bottleneck

A sharp reduction in population size that causes loss of genetic variation

Small population as a violation of HWE

Because genetic drift is strong, causing random changes in allele frequencies

Single seed descent

A plant breeding method where one seed from each plant is used to grow the next generation, rapidly advancing generations while increasing homozygosity

Types of cells that can be used for livestock genomic studies

A breeding method where one seed per plant is chosen each generation to quickly advance generations and fix traits

Value and functionality of hybrid crops

Higher yield, better uniformity, and improved vigor (hybrid vigor/heterosis), often with increased resistance to stress, pests, or disease

Two essential characteristics of a cultivar

Identity

reproducibility

Methods to identify heterotic groups

Field performance of crosses (diallel or test crosses)

Molecular markers / DNA analysis

Combining ability studies (GCA/SCA)

EPD in beef cattle

Expected Progeny Difference — predicts the genetic value a parent passes to its offspring for specific traits (e.g., weight, milk, fertility)

Order of size of DNA sequences during assembly

Short reads → contigs → scaffolds → chromosomes → whole genome

US federal agencies that regulate transgenic plants and animals

EPA

FDA

USDA

Definition of a GMO crop

A crop whose DNA has been artificially modified using genetic engineering to introduce or change specific traits.

Transgenic animal products that are commonly approved and available

Recombinant human insulin (from genetically engineered bacteria/animals used in production systems)

Antithrombin (from transgenic goats)

Clotting factors for hemophilia (from engineered organisms)

Some transgenic salmon approved for faster growth

Value and implementation of gene editing

Value: precise, fast improvement of traits (disease resistance, yield, quality)
Implementation: using tools like CRISPR to add, remove, or change specific DNA sequences in organisms

Selectable markers in plants that are the least problematic for comercialization

Non-antibiotic or removable markers, such as herbicide resistance markers (e.g., bar gene), or marker-free systems where the marker is removed after selection

Gene gun

A device that uses high pressure to shoot DNA-coated particles into plant cells to create genetic modification.

Why sunflowers and peanuts are not transgenic

they are commonly improved through traditional breeding, and transgenic versions are limited due to regulatory, market, and consumer acceptance issues