7.1 Chromosomes and Phenotype

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What are autosome chromosomes?

What are autosome chromosomes?

Chromosomes 1-22.

How many autosomes are there in a somatic cell?

There are 44 autosomes in a somatic cell.

What are sex chromosomes?

X and Y chromosomes.

How many zex chromosomes are in a somatic cell?

There are 2 sex chromosomes in a somatic cell.

What did Mendel study?

Mendel studied autosomal inheritance.

What are some examples of recessive diseases?

Tay Sachs, Cystic Fibrosis, and Sickle Cell Anemia.

What does it mean if a parent carries a recessive allele for a genetic disorder?

If a parent carries a recessive allele for a genetic disorder, they are heterozygous and said to be a "carrier".

What is the genotype of a carrier?

Aa, Bb, Rr etc.

How many copies of a recessive allele does someone have to have for a recessive phenotype to occur?

Two copies of the recessive allele.

What are some examples of dominant disorders?

Huntington Disease, Marfan Syndrome, and Osteogenesis Imperfecta.

How many copies of the dominant allele must someone have to express the phenotype?

One copy of the dominant allele.

What do sex-linked traits result from?

Sex-linked traits result from sex-linked genes that exist on sex chromosomes.

What chromosome do females provide to the offspring?

X chromosome.

What chromosome do males provide to the offspring?

X or Y chromosome.

Why is the x chromosome more "influential"?

It's larger and is thought to contain some genes that used to "belong" to the Y chromosome (became transferred during meiosis).

Where will sex-linked genes always be expressed?

All sex-linked genes, even recessive, will be expressed in males. Males are homozygous for that trait.

What is X chromosome inactivation?

When one X chromosome is randomly inactivated in each somatic cell.

What is an example of where X chromosome inactivation has occurred?

Calico cats - random cells have random X-linked gene expression.