Chapter 12

Question 1

Species

Answer 1

A group of individuals that share many characteristics an are able to interbreed under natural conditions to produce fertile offspring.

Question 2

Population

Answer 2

A group of organisms of the same species living together in a particular place at a particular time.

Question 3

Allele

Answer 3

An alternative form of a gene.

Question 4

Gene pool

Answer 4

Sum of all the alleles in a given population.

Question 5

Mutation

Answer 5

A change in a gene/chromosome leading to new characteristics in an organism.

Question 6

Gene

Answer 6

A section of DNA which codes for a protein (one characteristic).

Question 7

Gene mutation

Answer 7

An alteration to a single gene.

Question 8

Chromosome

Answer 8

Carries hereditary information, all human body cells have 23 pairs of chromosomes.

Question 9

Chromosomal mutation

Answer 9

Change to a structure and number of chromosomes in an organism.

Question 10

Mutagen OR mutagenic agents

Answer 10

Environmental agent that increases the rate of mutation.

Question 11

Somatic mutation

Answer 11

Occurring in a gene in a BODY CELL (not a gamete/sex cell).

Question 12

Germline mutation

Answer 12

A mutation in the gamete that becomes incorporated into the DNA of every cell in the body of the offspring.

Question 13

Point mutation

Answer 13

Change in just one of the bases in a DNA molecule.

Question 14

Trisomy

Answer 14

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).

Question 15

Monosomy

Answer 15

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.

Question 16

Mutant

Answer 16

An organism with a characteristic resulting from a mutation.

Question 17

Albinism

Answer 17

Absence of pigment in the hair, skin and eyes.

Question 18

Muscular dystrophy

Answer 18

Genetic disease resulting in wasting of leg muscles, then arms, shoulders and legs.

X-linked recessive..

Question 19

Cystic fibrosis

Answer 19

Disorder controlled by a recessive allele carried on an autosome that is incurable but can be detected during foetal development..

Question 20

Lethal recessive

Answer 20

Recessive alleles that result in the death of an embryo, foetus or child.

Question 21

Tay-Sachs (TSD)

Answer 21

Lethal recessive condition - a genetic disorder caused by a missing enzyme that results in fatty substances accumulating in the nervous system.

Question 22

Chromosomal mutations: Deletion

Answer 22

Part of a chromosome is lost.

Question 23

Chromosomal mutations: Duplication

Answer 23

A section of chromosome occurs twice.

Can occur if part of chromatid breaks off and joins onto the wrong chromatid.

Question 24

Chromosomal mutations: Inversions

Answer 24

Piece of chromosome breaks from the middle of a chromosome but when it reattaches - it’s the wrong way around.

Question 25

Chromosomal mutations: Translocation

Answer 25

Part of the chromosome breaks off - joining to the wrong chromosome.

Question 26

Chromosomal mutations: Non-disjunction

Answer 26

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.

Question 27

Patau syndrome

Answer 27

Trisomy of 13.

Symptoms: mental retardation, small head, cleft palette and extra fingers.

Question 28

Klinefelter’s syndrome

Answer 28

XXY - changes occur in puberty (males).

Small testes that don’t produce sperm, enlarged breasts and sparse body hair.

Question 29

Cri-du-chat syndrome

Answer 29

Missing part of chromosome 5 - partial monosomy.

Larynx problems.

Question 30

Turner’s syndrome

Answer 30

Having one X chromosome.

Symptoms: lacks secondary characteristics, short and infertile.

Question 31

Examples of mutagens?

Answer 31

UV light, cosmic rays, X-rays and nuclear fallout.

Question 32

Congenital disorder - caused by a gene mutation.

Answer 32

Dystrophy, cystic fibrosis, sickle-cell anaemia and Tay-Sachs.

Question 33

Congenital disorder - caused by a chromosomal mutation.

Answer 33

Down syndrome, Turner’s syndrome and Cri du chat.

Question 34

Why are mutations important?

Answer 34

Some may be harmful by they remain an important source of variation in evolution
Mutations can produce favourable variation

Question 35

Genotype?

Answer 35

Genetic makeup of an individual

Question 36

Phenotype?

Answer 36

Appearance of an organism