Genetics: Chapter 4 Exam 2 Prep

What is an allele?

An alternate form of a gene

What is a wild type allele?

The allele that occurs more frequently within a population. It is the allele that is deemed as normal or non unique.

Is a wild-type allele dominant or recessive.

Both. Wild- type alleles are often dominant, but can be recessive.

What is a mutation?

A change in the DNA sequence that results in an alternate version of a gene/allele.

According to Mendel, how are genes passed?

From parents to offspring

Do all allies have a dominant/recessive relationship?

No. Alleles are still passed from parents to offspring, but they are sometime not strictly dominant or recessive.

What is the relationship between alleles and genes?

Genes give the instruction for a trait while and an allele is an alternate version of that gene.

Gene—> Determines eye color. Allele—> is the eye color

How many genes can influence one trait?

2 or more genes can influence the phenotype of a single characteristic/trait.

What determines an organism’s phenotype?

Both genes and the environment

What is extra nuclear inheritance?

The inheritance of genes found in the mitochondria and chloroplast instead of the nucleus.

How are genes passed through extranulclear inheritance?

Through the mother’s egg.

How can phenotypic ratios differ from standard Mendelian crosses?

Some traits do not follow the inheritance patterns which can produce different phenotypic ratios.

What is passed from parents to offspring?

Genes

True or false: Alleles are strictly dominant

False. Sometimes alleles are neither strictly dominant or recessive.

What is a gene?

A section of DNA that gives instruction for a trait.

What is a mutant allele?

A allele that contains modified genetic information.

How are alleles created?

Through genetic mutation by altering the DNA sequence of a gene.

What must happen for a new allele to be recognized?

It must cause a change in the phenotype.

What is a loss of function mutation?

A mutation that causes a gene’s normal function to work less than normal or stop working all together.

Guess that mutation: causes a gene’s normal function to work less than normal or stop working all together.

Loss of function mutation

What is a null allele?

A gene product that has completely lost its function.

What is an extreme case of loss of function mutation?

A null allele

What is a gain of function mutation?

A mutation that enhances the function of a wild type allele and usually causes it to be dominant.

What is a gain of function mutation?

A mutation that enhances the function of a wild type allele and usually causes it to be dominant.

What is a neutral mutation?

When the genes produce no change to the phenotype.

What causes an intermediate phenotype?

Incomplete dominance

What is incomplete dominance?

What the mating of two Dominant parents produce an offspring that has a new phenotype that is a mix of both.

What is Complete Dominance?

What one allele completely masks the other.

What is Codominance?

When there is not dominance or recessiveness, it instead produces joint expression of both heterozygous alleles.

What ratio are you likely to see with Incomplete Dominance?

1:2:1

What are essential genes?

Genes that are absolutely required for survival.

What is a lethal allele?

An allele that has the potential to cause death.

Can you survive a lethal allele?

Yes, but only if it’s heterozygous recessive. If it’s homozygous, it will not survive.

What is polygenic inheritance?

Multiple genes affecting one trait

What is sex limited inheritance?

The idea that a gene can be present in both sexes but express only in one sex.

What are sex-linked genes?

Genes that are located on the x or Y chromosomes that make the inheritance pattern differ between men and women.