Chapter 14 Mendel and Gene idea

Homozygous meaning

organisms with two identical alleles for a particular gene

Heterozygous

An organism that has two different alleles for a trait

dominant allele

An allele whose trait always shows up in the organism when the allele is present.

recessive allele

An allele that is masked when a dominant allele is present

Genotype

An organism's genetic makeup, or allele combinations.

Phenotype

An organism's physical appearance, or visible traits.

monohybrid cross

A cross between individuals that involves one pair of contrasting traits

Punnett Square

A chart that shows all the possible combinations of alleles that can result from a genetic cross

Mendels's Law of segregation

Alleles on the chromosomes separate which describes the inheritance of a single characteristic.

homologous chromosomes

Chromosomes that have the same sequence of genes and the same structure

dihybrid cross

A cross between individuals that have different alleles for the same gene

Mendel's Law of Independent Assortment

the inheritance of one character has no effect on the inheritance of another

How is a testcross performed?

Cross the unknown genotype (A_) with aa (homozygous recessive)

Explain how the rule of multiplication can be used to determine the probability of an event?

Explain how the rule of addition can be used to determine the probability of an event?

Why was Mendel wise to use large sample sizes in his studies

Mendel knew that he needed to obtain large samples before he could begin to interpret inheritance patterns.

incomplete dominance

Situation in which one allele is not completely dominant over another allele

multiple allele inheritance

occurs when there are more than two different alleles of a gene for a particular trait

codominant alleles

Pairs of alleles that both affect the phenotype when present in a heterozygote

Pleiotropy

A single gene having multiple effects on an individuals phenotype (a syndrome) sickle cell anemia is an example

polygenic inheritance

combined effect of two or more genes on a single character.

What was the most significant conclusion that Gregor Mendel drew?

genes are inherited in discrete units and are not blended

An allele that exerts its effects whenever it is present is

dominant

The specific allele combination for a trait is referred to as the

genotype

Where two alternatives for a trait are tall and short and tall is dominant, the heterozygous individual would be written as:

Tt

What is indicated when a single character cross yields offspring that all express the dominant phenotype?

the parent with the dominant phenotype is homozygous

Which of the following is an example of polygenic inheritance?

skin color in humans