12. Mutations and gene pools Flashcards
what is a species?
a group of individuals that share many characteristics and are able to interbreed under natural conditions to produce fertile offspring
What are alleles?
alternative forms of a gene which determine the characteristics of an individual
What is a population?
a group of organisms of the same species living together in a particular place at a particular time
What are geneticists?
scientists who specialise in the study of inheritance
What is a gene pool?
the sum of all the alleles in a given population
What are allele frequencies?
how often each allele of a gene occurs in the gene pool for that population
why do the frequency of particular alleles in a population?
due to chance events (mutation that alters the expression of a gene) or natural events (changes in the environment may result in variations of the allele frequencies)
how can someone tell a mutation has occurred?
when an offspring shows variation that do not resemble either parent and have never occurred before
what is a mutant?
an organism with a characteristic resulting from a mutagen
what are the two types of mutations?
gene mutations and chromosomal mutations
What is a gene mutation?
changes in a single gene so that traits normally produced by the gene are changed or destroyed
What are chromosomal mutations?
all or part of a chromosome is affected
When do gene mutations occur?
during the replication of the DNA molecule before cell division
how is a mutation passed on from generation to generation?
when a cell divides, genetic information is usually passed on correctly
if a mistake occurs it will be faithfully be copied each time the DNA molecule replicates
hence the mutation is passed on from generation to generation
what are mutagens/ mutagenic agents?
agents that increase the rate at which mutations occur
what is a somatic mutation?
only the individual with the somatic mutation is affected
why are somatic mutations not passed down?
mutation is passed onto daughter cells
reproductive cells aren’t affected and once the individual dies, mutation is lost
somatic mutations are involved in many cancerous growths that may be a result of a mutagenic agent
what is a germinal/ germ-line mutation?
if reproductive cells are affected, the mutation may occur in the gametes and can be passed onto the subsequent generation
does a germinal mutation affect the individual in which the mutation occurs?
no they aren’t usually affected, the individual just produces gametes with changed DNA
however the embryo is usually naturally aborted in early pregnancy
what is a point mutation?
a change in just one base, could alter a protein, have no effect at all, or prevent the protein from being produced
if DNA of a particular gene is altered, the protein for which it codes for may be missing or abnormal
what type of mutation is albinism?
point mutation
result of one missed protein, it is marked by an absence of pigment from hair skin and eyes
what type of mutation is duchenne and how does it occur?
form of muscular dystrophy, is a gene mutation through the mother which is inherited by her sons
- also occurs in a male zygote so the child develops the disease
- disease results in a wasting of the leg muscles, arms, shoulders, and chest
what type of mutation is cystic fibrosis?
gene mutation on a huge gene on chromosome 7
- gene codes for 1480 amino acids that make up a protein that regulates the passage of chloride ions across the cell membrane
mutant allele is recessive so to suffer from it, a person must inherit the mutant allele from both parents
what are the types of chromosomal mutations?
deletion duplication inversion translocation non-disjunction
what is a deletion in chromosomal mutations?
part of a chromosome is lost
What is a duplication in chromosomal mutations?
a section of the chromosome occurs twice, this may happen if part of a chromatid breaks off and joins on the wrong chromatid
What occurs in an inversion in a chromosomal mutation?
breaks occur in a chromosome and the broken piece joins back in, but the wrong way around
-this changes the order of genes on the chromosome and may disrupt the pairing of homologous chromosomes during meiosis
what occurs in a translocation of a chromosomal mutation?
part of a chromosome breaks off and is rejoined to the wrong chromosome
what occurs in a non-disjunction mutation of a chromosomal mutation?
during meiosis, a chromosome pair does not separate and so one extra daughter cell has an extra chromosome and one daughter cell has less than normal
what occurs in the mutation for down syndrome (trisomy 21)
a child has 3 chromosome 21’s
a result of non-disjunction, the failure of one or more chromatids to separate in the second division of meiosis
What is a partial trisomy?
when an individual has part of an extra copy of chromosome 21 (eg) which is attached to one of the other chromosomes
what mutation occurs in patau syndrome?
trisomy 13 produces individuals with mental retardation, a small head, an extra finger on each hand, a cleft palate/lip and malformations of the ears and eyes
extra chromosome can either come from mothers egg of fathers sperm
what mutation occurs in klinefelters syndrome?
males- non disjunction during either first or second meotic division
produces individuals with either an extra X chromosome (XXY) or extra Y chromosome (XYY)
develops as adults
they have small testes, dont produce sperm, breasts are enlarged and body hair is sparce
what is a monosomy?
where an individual is missing a chromosome- only have one copy instead of 2
What occurs if an autosome is completely missing?
monosomy results in severe malformations and miscarriages
What happens in Cri-Du-Chat?
a rare genetic disorder due to a missing portion of chromosome 5
characteristics include a childs cry sounding like the meow of a cat due to problems with their larynx and nervous system
What does turners syndrome produce?
females that are short in stature, lack secondary sex characteristics and are infertile
frequently diagnosed before birth by analysing cells in the amniotic fluid or placenta
