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