mutations, genes and alleles - Unit 4 AOS 2

Question 1

gene

Answer 1

a section of DNA that carries a code to build a protein

Question 2

gene pool

Answer 2

the complete set of alleles present within a population

Question 3

population

Answer 3

a group of individuals of the same species living in the same location

Question 4

allele frequency

Answer 4

the proportion of certain alleles within a gene pool

Question 5

genetic diversity

Answer 5

The variation in genetic makeup or alleles within a population

Question 6

genotype

Answer 6

the genetic composition of an organism at a particular gene locus

Question 7

phenotype

Answer 7

the physical or biochemical characteristics of an organism that are the result of gene expression and the environment

Question 8

allele

Answer 8

alternate form of a gene

Question 9

mutation

Answer 9

• A gene mutation is a permanent change in the nucleotide sequence of a section of DNA that can give rise to new alleles
• they can happen either spontaneously or from a mutagen such as radiation or carcinogens
• they can be advantageous, deleterious or neutral

Question 10

germline vs somatic

Answer 10

• germline cells are cells involved in the generation of gametes in eukaryotes
• somatic cells are any cell in an
  organism that is not a germline cell

Only germ line mutations (in gametes) produce heritable variation, somatic mutations (in body cells) are not passed to offspring

Question 11

point mutations

Answer 11

Point mutations describe changes to a single nucleotide in a gene

Question 12

point mutation - silent mutation

Answer 12

• A silent mutation is a nucleotide substitution in DNA that does not result in a change in the amino acid sequence
  of polypeptide chain encoded by this gene.
• Due to the degenerate nature of the genetic code, multiple different codons code for the same amino acid and, therefore, despite a change to the original DNA sequence, the same amino acid is incorporated into the protein.

Question 13

point mutation - missense mutation

Answer 13

• Substitution mutations which code for a different amino acid, altering the primary
  structure of the polypeptide. This in turn affects the folding of the polypeptide and
  could alter the functioning of the protein

Question 14

point mutation - Nonsense mutation

Answer 14

• A nonsense mutation in DNA is a nucleotide substitution that changes a DNA triplet so that, instead of coding for
  an amino acid, it codes for a STOP signal, leading to a shortened protein product
• Due to the substitution of a nucleotide that causes the affected codon to become
  a stop codon, the gene will not be completely translated, leading to a polypeptide
  that is too short to function as intended. These mutations are generally considered
  the most dangerous.

Question 15

frameshift mutation

Answer 15

• nucleotides can be inserted or deleted, causing a the reading frame to shift
• all codons after the mutation will be changes, casing major changes in amino acids and thus the folding of the protein.

Question 16

block mutation

Answer 16

• Block mutations are chromosomal changes affecting large segments of a chromosome. These block mutations most commonly arise as a result of spontaneous errors in crossing over during meiosis, or they may be induced by mutagenic agents, such as x-rays

Question 17

changes to chromosomes

Answer 17

aneuploidy - when a cell or organism varies in the usual amount of chromosomes in its
genome by the addition or loss of a chromosome

polyploidy - when an organism contains additional sets of chromosomes in its genome