Chapter 23-24 Genetics Outline Flashcards
What is a Phenotype?
Physical appearance trait
What is a Genotype
Alleles responsible for given trait
What is the characteristic of the Dominant allele?
- Is capitalized
- Is physically apparent
What is the characteristic of the Recessive allele?
- Is lowercased
- Not physically apparent; dormant
What is a Homologous Chromosome?
Each PAIR of MATCHING chromosomes (homo=same)
How many pairs of chromosomes do humans have?
23 chromosomes.
23 maternal + 23 paternal = 46 chromosomes
What happens to homologous chromosomes during meiosis?
They separate
Homozygous
Both alleles are the same
Heterozygous
The two alleles are different
Monohybrids
Heterozygous for one pair of alleles
Genotype ratio
1 WW
2 Ww
1 ww
1:2:1
Phenotype ratio
3:1
What’s the probability of inheritance in 1-Trait crosses?
- The chance of two or more independent events
- Product of all chances
What does a Punnett Square do?
Writes out every possibility
What is a Dihybrid?
Individual that is heterozygous for two traits (a carrier of two traits)
What is a Dihybrid Cross?
Cross between two individuals heterozygous for 2 traits
When does Incomplete Dominance occur?
It occurs when the heterozygote (HsHc) is INTERMEDIATE between the two homozygotes
When does Codominance occur?
It occurs when alleles are EQUALLY expressed in a heterozygote
What is Multiple Allele Inheritance?
The gene exists in several allelic forms
Each individual has only two of the possible alleles
What can influence the expression of genetic traits?
Environmental factors
Describe Sex-linked Inheritance
Humans have 23 pairs of chromosomes.
- 22 pairs of autosomes
- 1 pair of sex-chromosomes (X and Y)
What is a Sex-linked Trait?
Trait controlled by genes on the sex chromosomes
What are Sex-linked Alleles?
Alleles on the sex chromosome
Xb
colorblindness
