Genetics Flashcards
(20 cards)
What is a Gene?
Section of DNA that codes for proteins
Genes are the basic units of heredity in living organisms.
Define Alleles
Different forms of a gene; either dominant or recessive
Alleles can affect the phenotype of an organism.
What is a Chromosome?
Structure made up of DNA and proteins
Chromosomes carry genetic information.
Define Genotype
Genetic makeup of an organism (ex. AA, Aa, aa)
Genotype determines potential traits but not their expression.
What is a Phenotype?
Visible expression of genetic makeup; physical traits (ex. blue eyes)
Phenotype can be influenced by environmental factors.
Define Homologous chromosomes
Pair of chromosomes that contain genes for the same traits; one from mom and one from dad
Homologous chromosomes may carry different alleles.
What does Homozygous mean?
Possesses identical alleles for a given gene on homologous chromosomes (ex. AA or aa)
Also known as true-breeding.
Define Heterozygote
Possesses different alleles for a given gene on homologous chromosomes (ex. Aa)
Also known as hybrids.
What are Sex chromosomes?
Determine the sex of an individual; in humans, X and Y chromosomes
XY for males, XX for females.
Define Autosome
Chromosome that is not a sex chromosome
Autosomes are present in both sexes.
What is the P generation?
Individuals for initial cross
This generation is the starting point for genetic crosses.
Define F1 generation
Offspring from initial cross
F1 generation is often heterozygous for traits.
What is the F2 generation?
Offspring that results from cross of F1 individuals
The F2 generation can show a variety of phenotypes.
Define Dominant allele
Masks recessive allele; expressed in homozygous dominant and heterozygous conditions
Represented by capital letters (i.e. A, B, H, L).
What is a Recessive allele?
Not expressed in heterozygous condition; expressed only when individual is homozygous for the allele
Represented by lowercase letters (i.e. a, b, h).
Define Monohybrid cross
Only one trait is involved (ex. Bb x Bb)
It examines the inheritance of a single characteristic.
What is a Dihybrid cross?
Two or more traits are involved (ex. BbSs x BbSs)
It examines the inheritance of multiple characteristics.
Define Incomplete dominance
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).
What is Codominance?
Both alleles are expressed
Example: A red cow (RR) crossed with a white cow (WW) produces a white AND red cow (RW).
Define Multiple alleles
More than two alleles exist for a trait
Example: Human blood types have three possible alleles (IA, IB, and i).
