Genetics

Question 1

What is a Gene?

Answer 1

Section of DNA that codes for proteins

Genes are the basic units of heredity in living organisms.

Question 2

Define Alleles

Answer 2

Different forms of a gene; either dominant or recessive

Alleles can affect the phenotype of an organism.

Question 3

What is a Chromosome?

Answer 3

Structure made up of DNA and proteins

Chromosomes carry genetic information.

Question 4

Define Genotype

Answer 4

Genetic makeup of an organism (ex. AA, Aa, aa)

Genotype determines potential traits but not their expression.

Question 5

What is a Phenotype?

Answer 5

Visible expression of genetic makeup; physical traits (ex. blue eyes)

Phenotype can be influenced by environmental factors.

Question 6

Define Homologous chromosomes

Answer 6

Pair of chromosomes that contain genes for the same traits; one from mom and one from dad

Homologous chromosomes may carry different alleles.

Question 7

What does Homozygous mean?

Answer 7

Possesses identical alleles for a given gene on homologous chromosomes (ex. AA or aa)

Also known as true-breeding.

Question 8

Define Heterozygote

Answer 8

Possesses different alleles for a given gene on homologous chromosomes (ex. Aa)

Also known as hybrids.

Question 9

What are Sex chromosomes?

Answer 9

Determine the sex of an individual; in humans, X and Y chromosomes

XY for males, XX for females.

Question 10

Define Autosome

Answer 10

Chromosome that is not a sex chromosome

Autosomes are present in both sexes.

Question 11

What is the P generation?

Answer 11

Individuals for initial cross

This generation is the starting point for genetic crosses.

Question 12

Define F1 generation

Answer 12

Offspring from initial cross

F1 generation is often heterozygous for traits.

Question 13

What is the F2 generation?

Answer 13

Offspring that results from cross of F1 individuals

The F2 generation can show a variety of phenotypes.

Question 14

Define Dominant allele

Answer 14

Masks recessive allele; expressed in homozygous dominant and heterozygous conditions

Represented by capital letters (i.e. A, B, H, L).

Question 15

What is a Recessive allele?

Answer 15

Not expressed in heterozygous condition; expressed only when individual is homozygous for the allele

Represented by lowercase letters (i.e. a, b, h).

Question 16

Define Monohybrid cross

Answer 16

Only one trait is involved (ex. Bb x Bb)

It examines the inheritance of a single characteristic.

Question 17

What is a Dihybrid cross?

Answer 17

Two or more traits are involved (ex. BbSs x BbSs)

It examines the inheritance of multiple characteristics.

Question 18

Define Incomplete dominance

Answer 18

No allele completely dominates another; results in a phenotype intermediate to that of parents

Example: A red flower (RR) crossed with a white flower (WW) produces pink flowers (RW).

Question 19

What is Codominance?

Answer 19

Both alleles are expressed

Example: A red cow (RR) crossed with a white cow (WW) produces a white AND red cow (RW).

Question 20

Define Multiple alleles

Answer 20

More than two alleles exist for a trait

Example: Human blood types have three possible alleles (IA, IB, and i).