2C Gene expression and GENETICS

Question 1

types of point mutation

Answer 1

• substitution
• deletion
• insertion

Question 2

substitution mutation

Answer 2

type of point mutation; one base in a gene is substituted for another

Question 3

deletion mutation

Answer 3

type of point mutation; a base is completely lost

Question 4

insertion mutation

Answer 4

type of point mutation; an extra base is added into a gene

Question 5

mutation

Answer 5

a permanent change in the DNA of an organism

Question 6

gametes

Answer 6

haploid sex cells that fuse to form a new diploid cell (zygote) in sexual reproduction

Question 7

chromosomal mutations

Answer 7

changes in the position of entire genes within a chromosome

Question 8

whole-chromosome mutations

Answer 8

the loss of duplication of a whole chromosome
• e.g. down syndrome is caused by a whole-chromosome mutation at chromosome 21

Question 9

mutagent

Answer 9

anything that increases the rate of mutation
e.g. X-rays, ionising radiation

Question 10

variation

Answer 10

difference between organisms which may be the result of different genes or the environment they live in

Question 11

phenotype

Answer 11

the physical traits, including biochemical characteristics, expressed as a result of the interactions of the genotype with the environment

Question 12

genotype

Answer 12

the genetic make-up of an organism with respect to a particular feature

Question 13

homologous pairs

Answer 13

matching pairs of chromosomes in an individual which both carry the same genes, although they may have different alleles

Question 14

locus

Answer 14

the site of a gene on a chromosome

Question 15

alleles

Answer 15

versions of a gene, variants

Question 16

homozygote

Answer 16

an individual where both alleles coding for a particular characteristic are identical

Question 17

heterozygote

Answer 17

an individual where the two alleles coding for a particular characteristic are different

Question 18

dominant

Answer 18

a characteristic which is expressed in the phenotype whether the individual is homozygous or heterozygous for that allele

Question 19

recessive

Answer 19

a characteristic which is only expressed when both alleles code for it; in other words, the individual is homozygous for the recessive trait

Question 20

true breeding

Answer 20

a homozygous organism which will always produce the same offspring when crossed with another true-breeding organism for the same characteristic

Question 21

monohybrid cross

Answer 21

a genetic cross where only one gene for one characteristic is considered

Question 22

monohybrid cross

Answer 22

a genetic cross where only one gene for one characteristic is considered

Question 23

codominance

Answer 23

in heterozygotes, where both alleles at a gene locus are fully expressed in the phenotype

Question 24

sex-linked traits

Answer 24

characteristics which are inherited on the sex chromosomes

Question 25

autosomes

Answer 25

chromosomes which carry information about the body but do not determine the sex of an individual

Question 26

homogametic

Answer 26

an individual who produces gametes that contain only one type of sex chromosome - in humans this is the female

Question 27

heterogametic

Answer 27

an individual who produces two types of gamete each containing different types of sex chromosome - in humans this is the male

Question 28

transcription factors

Answer 28

proteins that bind to the DNA in the nucleus and affect the process of converting, or transcribing, DNA into RNA

Question 29

epigenetics

Answer 29

the study of changes in gene expression (active versus inactive genes) that does not involve changes to the underlying DNA sequence but affects how cells read genes

Question 30

sex-linked diseases

Answer 30

genetic diseases that result from a mutated gene carried on the sex chromosomes - ir human beings, on the X chromosome

Question 31

red-green colour blondness

Answer 31

a sex-linked genetic condition which affects the ability to distinguish tones of red and green

Question 32

haemophilia

Answer 32

a sex-linked genetic disease in which one of the factors needed for blood to clot is not made in the body

Question 33

genetic screening

Answer 33

when whole populations are tested for a genetic disease

Question 34

phenylketonuria PKU

Answer 34

a recessive genetic disorder where those affected lack the enzyme needed to digest the amino acid phenylalanine; the amino acid builds up in the blood and causes severe brain damage

Question 35

parental screening

Answer 35

screening of an embryo or fetus before birth

Question 36

amniocentesis

Answer 36

a type of prenatal screening which involves removing a sample of amniotic fluid at around 16 weeks of pregnancy, culturing the fetal cells found and analysing them for genetic diseases

Question 37

chorionic villus sampling

Answer 37

a type of prenatal screening where a small sample of embryonic tissue is taken from the developing placenta and the cells tested for genetic diseases

Question 38

preimplantation

Answer 38

genetic diagnosis testing the cells of an embryo produced by IVF to check for genetic diseases before it is implanted into the uterus of the mother

Question 39

PKU

Answer 39

phenylketonuria

Question 40

At what point during the pregnancy are amniocenteses performed?

Answer 40

at about the 16th week of pregnancy

Question 41

when during pregnancy is a chorionic villus sampling performed?

Answer 41

at about 8-10 week of pregnancy

Question 42

why do most mutations have no observable effects on the organism?

Answer 42

- the mutations occur in part of the non-coding DNA which does not affect the way the genetic code is read - the code is degenerate, and one small change in the code may not alter the amino acid coded for

Question 43

what are the two types of chromosomes found in cells?

Answer 43

autosomes and sex chromosomes