6.7: Mutations

Question 1

How does the genotype influence the phenotype?

Answer 1

The gene codes for proteins, which help to influence the phenotype of the organism.

Question 2

How do new phenotypes originate?

Answer 2

Disruptions in genes and gene products.

Question 3

How do mutations affect gene products?

Answer 3

Mutations change the genome of the organism. Any products of this mutated gene would fold differently, resulting in a different function.

Question 4

What are the three types of substitution point mutations? How does each affect the protein product? How does each affect the amount of the protein product?

Answer 4

neutral-the substitution does not result in a change in amino acids
positive-codes for a protein that is beneficial to the organism.
negative-codes for a protein that is detrimental to the organism.

Question 5

What happens if an insertion or deletion occurs at a nucleotide base pair?

Answer 5

They could cause a frame shift that would code for multiple different amino acids. It could cause an early stop codon so not all gets translated. It could cause a start codon to not be translated, so the entire sequence would be lost.

Question 6

What causes errors in DNA replication?

Answer 6

Radiation, chemicals, toxins, mutagens, which result in incorrect nucleotide pairing.

Question 7

What is involved in the cell’s DNA repair mechanisms?

Answer 7

Enzymes are used in order to remove and replace incorrectly paired nucleotides. Nuclease cuts the DNA strand. Tehn DNA polymerase and codes for the new nucleotides and DNA ligase reconnects the DNA strand.

Question 8

What is the cause of new genetic variation?

Answer 8

The processing of genetic information (error replication, repair, radiation, chemicals)

Question 9

Identify an error in mitosis that leads to a change in phenotype.

Answer 9

Chromosomes not separating in mitosis (nondisjunction) can lead to an increase in the amount of chromosomes in one cell and not enough in the other cell. -triploidy

Question 10

Identify an error in meiosis that leads to a change in phenotype.

Answer 10

Nondisjunction of homologous chromosome pairs.

Question 11

What does it mean if an organism is a triploid?

Answer 11

They have 3 sets of chromosomes.

Question 12

How do triploids form?

Answer 12

By nondisjunction

Question 13

Why is a triploid organism usually sterile?

Answer 13

They don’t have enough homologous chromosomes to be able to complete meiosis.

Question 14

What causes Down syndrome/Trisomy 21?

Answer 14

Chromosome 21 has an extra chromosome.

Question 15

What causes Turner syndrome?

Answer 15

A missing X chromosome.

Question 16

How does a change in genotype affect the phenotype?

Answer 16

A change in genotype causes a change in the phenotype of the organism.

Question 17

True or False: Natural selection acts on genotype.

Answer 17

True

Question 18

How does natural selection affect phenotypes and genotypes?

Answer 18

It selects for the phenotypes that are the most advantageous in a certain environment over generations.

Question 19

How does a genetic change enhance survival?

Answer 19

The more genetic variation, the more likely that the organism is able to survive and reproduce, so the chance of survival is greater.

Question 20

What is horizontal transfer?

Answer 20

The exchange of genetic information between different genomes or between unrelated organisms. (prokaryotes)

Question 21

How does horizontal transfer increase variation?

Answer 21

It exchanges portions of genomes, making both of them genetically different, therefore increasing genetic variation.

Question 22

What is transformation?

Answer 22

Uptake of naked DNA from outisde of the organism (DNA not protected by proteins or other molecules)-prokaryotes

Question 23

What is transduction?

Answer 23

Transmission of foreign DNA into a cell (viral genome incorporated into host genome)

Question 24

What is conjugation?

Answer 24

Cell to cell transfer of DNA.

Question 25

What is transposition?

Answer 25

movement of DNA segments within and between DNA molecules

Question 26

How do viruses recombine genetic information?

Answer 26

More than one virus infects the cell. Then, the genomes combine in the host cell when the information replicates.

Question 27

What reproductive processes increase genetic variation?

Answer 27

sexual reproduction (combination of random gametes), independent assortment of homologous pairs (don’t know which chromosomes will end up where), and crossing over during meiosis.