Chapter 23 Flashcards
What do chromosomes come in?
Pairs called homologous chromosomes.
Where are the members of the pairs of homologous chromosomes inherited from?
The mother, and the father.
What are some characteristics of homologous pairs?
Both members have same length and centromere location, both carry similar types of genes, alternate forms of a gene for a trait are called alleles, and they are always on the same spot.
What are some examples of alleles?
Tail length, eye colour.
What is a phenotype?
An individual’s actual appearance that includes physical characteristics or metabolic characteristics.
What is a genotype?
Alleles carried by the chromosomes that are responsible for a given trait.
How do you symbolize a dominant allele?
A capital letter.
How do you symbolize a recessive allele?
A lowercase letter.
What is homozygous?
If the 2 alleles are the same.
What is heterozygous?
If the 2 alleles are different.
How many alleles does a genotype have for a trait?
2
How many alleles does a gamete have for a trait?
1
A homozygous man with freckles reproduces with a woman without freckles, will their children have freckles?
Yes (Ff)
What are the steps used to solve a genetic cross.
- Determine the genotype of each parent.
- List the possible gametes from each parent.
- Combine all possible gametes.
- Determine the genotypes and phenotypes of all offspring.
Can you determine by observation if an individual expressing dominant trait is homozygous or heterozygous?
No.
How are homologous chromosomes inherited?
As a pair, one member from each parent.
During meiosis, what does each gamete receive?
One member of each pair of homologoues.
How do homologues separate?
Independently.
What is the law of independent assortment?
Each pair of factors assorts independently. All possible combinations of factors can occur in the gametes.
What is a dihybrid cross?
Used to test the law of independent assortment.
What things are often genetic in origin?
Many traits and disorders in humans and other organisms.
What are the genetic traits controlled by?
A single allele pair on the autosomal chromosomes, any chromosome other than (X or Y).
What is pedigree?
A chart of family’s history with regard to a particular genetic trait. It is used to determine whether inherited condition is due to autosomal dominant or autosomal recessive allele.
What do autosomal recessive disorders require?
The inheritance of two recessive alleles to display the disorder.
What are some examples of autosomal recessive disorders?
Sickle cell disease, cystic fibrosis.
What is an example of an autosomal dominant disorder?
Huntington disease.
Describe incomplete dominance.
Occurs when the heterozygote has an intermediate phenotype between the two homozygotes.
What is codominance?
Occurs when alleles are equally expressed in a heterozygote.
What happens when a trait is controlled by multiple alleles?
The gene exists in several allelic forms. Each person has only 2 of the possible alleles.
When does polygenetic inheritance occur?
When a trait is governed by two or more genes.
What do dominant alleles have a quantitative effect on?
The phenotype, and the effects are additive.
What is the result of the quantitative effect from dominant alleles?
Continuous variation of phenotypes. Example: skin colour.
What is an example of polygenetic inheritance?
General size.
What can influence the expression of genetic traits?
Environmental factors like nutrition or temperature.
What are polygenic traits especially influenced by?
Environment.
