chapter 19

Mutations can occur in somatic cells and in germ line cells. Which of these would be passed to offspring? Which of these can result in a genetic mosaic? What is a genetic mosaic? Give examples.

-germ line cell mutations would be passed to offspring -somatic cell mutations would result in a genetic mosaic -a genetic mosaic is a somatic region that where the skin is genotypically different form each other such as large birth marks

Describe how a mutation can affect the coding sequence within a gene. Know what happens in the case of silent mutations, missense mutations, nonsense mutations and frameshift mutations. Given one of these situations and a codon table, be able to predict the effect on the protein the gene codes for.

-silent mutation: are those base substitutions that do not alter the amino acid sequence of the polypeptide -missense mutation: are those base substitutions in which an amino acid change does occur -nonsense mutation: are single base substitutions that change a normal codon to a stop codon -frameshift mutation: involve the addition or deletion of a number of nucleotides that is not divisible by three which shifts the reading frame so that translation of the mRNA results in a completely different amino acid sequence downstream of the mutation

What is the difference between a spontaneous mutation and an induced mutation? Which can be caused by lifestyle?

-spontaneous mutation: result of errors in natural biological processes -induced mutation: are due to agents in the environment that cause changes in DNA structure

Be able to use the terms wild-type, mutant allele, reversion allele, deleterious mutation, lethal mutation, beneficial mutation and conditional mutations. Give examples.

-wild type- relatively prevalent genotype -mutant allele- not supposed to be there -reversion allele- changes a mutant allele back to the wild- type -deleterious mutation-decrease the chances of survival aka sickle cell anemia -lethal mutation-decrease the chances of survival aka malaria -beneficial mutation-enhance the survival or reproductive success of an organism peppered moth -conditional mutation-affect the phenotype only under a defined set of conditions aka temperature sensitive mutation

What is a mutation? What effects can these have on alleles of genes?

1. a heritable change in the genetic material 2. they can cause no change in the trait that is presented or they can be harmful

Discern between the two types of base substitutions: transitions and transversions

BOTH TYPES OF POINT MUTATIONS -transition: switches from a purine to another purine and a pyrimidine to another pyrimidine -transversion: switches from a purine to a pyrimidine or a pyrimidine to a purine

C14 Discuss the consequences of a germ-line versus a somatic mutation.

If a mutation within the germ line is passed to an offspring, all of the cells of the offspring's body will carry the mutation. A somatic mutation affects only the somatic cell in which it originated and all of the daughter cells that the somatic cell produces. If a somatic mutation occurs early during embryonic development, it may affect a fairly large region of the organism. Because germ-line mutations affect the entire organism, they are potentially more harmful (or beneficial), but this is not always the case. Somatic mutations can cause quite harmful effects, such as cancer.

C2 A gene mutation changes an AT base pair to GC. This change causes a gene to encode a truncated protein that is nonfunctional. An organism that carries this mutation cannot survive at high temperatures. Make a list of all the genetic terms that could be used to describe this type of mutation.

It is a gene mutation, a point mutation, a base substitution, a transition mutation, a deleterious mutation, a mutant allele, a nonsense mutation, a conditional mutation, and a temperature-sensitive lethal mutation.

Describe how a mutation can affect gene expression if the mutation occurs outside the coding region of a gene.

Mutations in the core promoter can change levels of gene expression which result in up mutations and down mutations

C8 A point mutation occurs in the middle of the coding sequence for a gene. Which types of mutations - silent, missense, nonsense, and frameshift - would be most likely to disrupt protein function and which would be least likely?

Nonsense and frameshift mutations would be most likely to disrupt protein function. A nonsense mutation would cause the protein to be much shorter, and a frameshift mutation would alter the amino acid sequence downstream from the mutation. A missense mutation only affects a single amino acid, so it is less likely to disrupt protein function, but it could alter a protein's function if it occurred in an important region of the protein. A silent mutation would not alter protein function.

C4 How would each of the following types of mutations affect protein function or the amount of functional protein that is expressed from a gene? a. nonsense mutation b. missense mutation c. up promoter d. mutation that affects splicing

a. a nonsense mutation would probably inhibit protein function, particularly if it was not near the end of the coding sequence b. a missense mutation may or may not affect protein function, depending on the nature of the amino acid substitution and whether the substitution is in a critical region of the protein. c. an up promoter mutation would increase the amount of functional protein d. this mutation may affect protein function if the alteration in splicing changes an exon in the mRNA that results in a protein with a perturbed structure

A mutation changes a codon that specifies tyrosine into a stop codon. This type of mutation is a a. missense mutation b. nonsense mutation c. frameshift mutation d. neutral mutation

b. nonsense mutation

A down promoter mutation causes the promoter of a gene to be __________ like the consensus sequence and __________ transcription. a. less, stimulates b. more, stimulates c. less, inhibits d. more, inhibits

c. less, inhibits

Which of the following is an example of a somatic mutation? a. a mutation in an embryonic muscle cell b. a mutation in a sperm cell c. a mutation in an adult nerve cell d. both a and c are examples of somatic mutations

d. both a and c are examples of somatic mutations

Which nitrogenous bases are purines and which are pyrimindines?

purines: adenine and guanine pyrimidines: cytosine, thymine, uracil