Chapter 12 Flashcards
Species
A group of individuals that share many characteristics an are able to interbreed under natural conditions to produce fertile offspring.
Population
A group of organisms of the same species living together in a particular place at a particular time.
Allele
An alternative form of a gene.
Gene pool
Sum of all the alleles in a given population.
Mutation
A change in a gene/chromosome leading to new characteristics in an organism.
Gene
A section of DNA which codes for a protein (one characteristic).
Gene mutation
An alteration to a single gene.
Chromosome
Carries hereditary information, all human body cells have 23 pairs of chromosomes.
Chromosomal mutation
Change to a structure and number of chromosomes in an organism.
Mutagen OR mutagenic agents
Environmental agent that increases the rate of mutation.
Somatic mutation
Occurring in a gene in a BODY CELL (not a gamete/sex cell).
Germline mutation
A mutation in the gamete that becomes incorporated into the DNA of every cell in the body of the offspring.
Point mutation
Change in just one of the bases in a DNA molecule.
Trisomy
A chromosomal mutation in which there are three chromosomes instead of a pair -> Down syndrome aka trisomy 21 (an extra copy on the 21st chromosome).
Monosomy
A chromosomal mutation in which there is 1 chromosome instead of a pair -> e.g Turner’s syndrome - only one X chromosome (in females).
If only part is missing = partial monosomy.
Mutant
An organism with a characteristic resulting from a mutation.
Albinism
Absence of pigment in the hair, skin and eyes.
Muscular dystrophy
Genetic disease resulting in wasting of leg muscles, then arms, shoulders and legs.
X-linked recessive..
Cystic fibrosis
Disorder controlled by a recessive allele carried on an autosome that is incurable but can be detected during foetal development..
Lethal recessive
Recessive alleles that result in the death of an embryo, foetus or child.
Tay-Sachs (TSD)
Lethal recessive condition - a genetic disorder caused by a missing enzyme that results in fatty substances accumulating in the nervous system.
Chromosomal mutations: Deletion
Part of a chromosome is lost.
Chromosomal mutations: Duplication
A section of chromosome occurs twice.
Can occur if part of chromatid breaks off and joins onto the wrong chromatid.
Chromosomal mutations: Inversions
Piece of chromosome breaks from the middle of a chromosome but when it reattaches - it’s the wrong way around.
Chromosomal mutations: Translocation
Part of the chromosome breaks off - joining to the wrong chromosome.
Chromosomal mutations: Non-disjunction
When eggs and sperm are formed - sometimes chromatid pairs do not move to separate cells.
One cell receives both chromatids and will have an extra chromosome, while the other cell will be one chromosome short.
Patau syndrome
Trisomy of 13.
Symptoms: mental retardation, small head, cleft palette and extra fingers.
Klinefelter’s syndrome
XXY - changes occur in puberty (males).
Small testes that don’t produce sperm, enlarged breasts and sparse body hair.
Cri-du-chat syndrome
Missing part of chromosome 5 - partial monosomy.
Larynx problems.
Turner’s syndrome
Having one X chromosome.
Symptoms: lacks secondary characteristics, short and infertile.
Examples of mutagens?
UV light, cosmic rays, X-rays and nuclear fallout.
Congenital disorder - caused by a gene mutation.
Dystrophy, cystic fibrosis, sickle-cell anaemia and Tay-Sachs.
Congenital disorder - caused by a chromosomal mutation.
Down syndrome, Turner’s syndrome and Cri du chat.
Why are mutations important?
Some may be harmful by they remain an important source of variation in evolution
Mutations can produce favourable variation
Genotype?
Genetic makeup of an individual
Phenotype?
Appearance of an organism
