Biology Chapter 8.2 Study Guide

Widow's peak and hitchhiker's thumb are multiple allele traits.

False

Single-gene X-linked traits have a different pattern of inheritance than single-gene autosomal traits because...

Males have just one X chromosome

Genetic Disorders...

Many genetic disorders are caused by mutations in one or a few genes, some genetic disorders are caused by abnormal numbers of chromosomes.

Nondisjunction occurs during -------

Meiosis

Because it is a polygenic trait, human height can be represented by a bell-shaped graph.

True

Down syndrome is also known as trisomy 21.

True

Epistasis is when one gene affects the expression of another gene.

True

Most human traits have more complex modes of inheritance than simple Mendelian inheritance.

True

Single-gene X-linked traits have a different pattern of inheritance than single-gene autosomal traits.

True

Pleiotropy

When a single gene affects more than one trait

Epistasis

When one gene affects the expression of another gene

In a polygenic trait, such as adult height, most people

Will have a phenotype close to the average

Sex-linked traits are usually associated with genes on the -------- chromosome

X

An example of a recessive -------- trait would be red-green color blindness

X-linked

ABO blood type is a multiple allele trait. With this information, are A, B, AB, and O possible?

Yes

A mother has red-green color blindness. Her husband is not affected. This means...

All of their sons will have red-green color blindness

Traits controlled by a single gene with more than two alleles are called multiple ------- traits

Allele

Triple X syndrome results in XYXX males.

False

What is always expressed in males?

A recessive X-linked allele

Pleiotropy is when a more than one gene affects a single trait.

False

ABO blood type

An example of a multiple allele trait

Genetic trait

Characteristics (traits) encoded in DNA

The alleles for ABO blood type are the A, B, AB and O alleles.

False

Explain what causes chromosomal disorders.

Chromosomal disorders are caused by nondisjunction, which is the failure of replicated chromosomes to separate during meiosis. Some of the resulting gametes will be missing a chromosome, while others will have an extra copy of the chromosome.

Hemophilia A results in reduced activity of a protein needed for blood -------

Clotting

------ is caused by an extra copy of chromosome 21

Down Syndrome

Describe the cause and symptoms of Down syndrome.

Down syndrome results from an extra copy (complete or partial) of chromosome 21. Individuals with Down syndrome experience developmental delays, distinctive facial appearance, and other abnormalities.

Amniocentesis can be used to see if the mother has any genetic abnormalities.

False

Characteristics that are encoded in DNA are called genetic diseases.

False

Most genetic disorders are controlled by dominant alleles.

False

Why are few genetic disorders controlled by dominant alleles?

Few genetic disorders are controlled by dominant alleles, because a mutant dominant allele would be expressed in every individual who inherits even one copy of it. If it causes a serious disorder, affected people may die young and fail to reproduce. Therefore, the mutant dominant allele is likely to die out of the population.

Mendelian inheritance refers to the inheritance of traits controlled by a single -------- with two ---------

Gene, alleles

What two main ways cause genetic disorders?

Genetic disorders are either caused by mutations in one or a few genes, or they are caused by abnormal numbers of chromosomes.

Sickle cell anemia results in an abnormal ------ protein in red blood cells

Hemoglobin

Gene therapy

Involves inserting normal genes into cells with mutant genes

ABO blood type is a -------- allele trait

Multiple

Many genetic disorders are caused by -------- in one or few genes

Mutations

Down syndrome is due to...

Nondisjunction of chromosome 21

Human height is an example of a ------ trait

Polygenic

X-linked trait

Red-green color blindness

Hemophilia A is due to...

Reduced activity of a protein needed for blood clotting.

Pedigree

Shows how a trait is passed from generation to generation within a family

What are the signs and symptoms of sickle cell anemia?

Sickle-shaped red blood cells that clog tiny blood vessels, causing pain and damaging organs and joints.

Nondisjunction

The failure of replicated chromosomes to separate during meiosis

Mendelian inheritance

The inheritance of traits controlled by a single gene with two alleles

Autosomal trait

Trait controlled by a gene on one of the 22 human autosomes

Sex-linked trait

Trait controlled by genes on the sex chromosomes

Characteristics that are encoded in DNA are called genetic --------

Traits

Multiple allele trait

Traits controlled by a single gene with more than two alleles

A karyotype is a picture of a cell's chromosomes.

True

A mutant recessive allele is not expressed in people who inherit just one copy of it.

True

A recessive X-linked allele is always expressed in males.

True