3 Inheritance Flashcards

Question

PAPER 2 What is transcription?

Answer 1

mRNA copies the sequence of bases of a section of DNA: Two strands of DNA helix are unzipped - caused by enzyme helicase The enzyme RNA polymerase attaches to DNA just before gene RNA polymerase moves along the DNA strand RNA polymerase catalyses the formation of covalent bonds between RNA nucleotides to form a strand of mRNA strand of mRNA is opposite copy of DNA strand (except U replaces T) - called complementary copy mRNA leaves nucleus to go to ribosome

Answer 2

for every 3 mRNA bases (codon) the ribosome lines up one complementary molecule of tRNA (complementary 3 bases of tRNA called anticodon) tRNA picks up specific amino acids from cytoplasm and transports to ribosome ribosome allows two tRNA molecules to sit next to each other ribosome catalyses the formation of a peptide bond between 2 amino acids chain of several hundred amino acids forms in specific order polypeptide folded into correct shape and becomes a specific protein

Answer 3

Transcription Translation

Answer 4

ribosomes in cytoplasm

Answer 5

alternative form of a gene (version of a gene) - controls characteristics e.g. allele for tall plant. allele for dwarf plant

Answer 6

specific gene, found on chromosomes the genes have two different forms called alleles

Answer 7

both chromosomes have the same allele (tt, TT)

Answer 8

one allele

Answer 9

A dominant allele only needs one allele present to be expressed

Answer 10

a recessive allele needs two alleles present to be expressed

Answer 11

both contain one of each allele (Tt, Tt)

Answer 12

what is expressed e.g. tall or dwarf

Answer 13

combination of alleles e.g. TT or Tt

Answer 14

characteristics controlled by several genes which influence each other

Answer 15

polygenic inheritance

Answer 16

Three phenotypes possible even though only two alleles: two alleles equally expressed

Answer 17

phenotype: red genotype: PᴿPᴿ phenotype: white genotype: PᵂPᵂ phenotype: pink genotype: PᴿPᵂ

Answer 18

genotypes of parents and offspring phenotypes of parents and offspring alleles found in each gamete probability of each phenotype in offspring (fraction of ratio)

Answer 19

Heterozygous parents: faulty gene = recessive, do not have disease but carry an allele therefore carriers 1st child = no disease 2nd and 3rd = carriers 4th child = has disease 25% chance of child with homozygous recessive so suffers from disease

Answer 20

Disease is recessive each parent had one copy of faulty allele so daughter would have inherited one allele from each parent genotype = heterozygous

Answer 21

50:50 Parents phenotypes: female, male parents genotypes: XX, XY gametes genotypes: X,X,X,Y Offsprings genotypes: XX,XX,XY,XY Offsprings phenotypes: female, female, male, male

Answer 22

Following sexual reproduction, or mutation, organisms have different versions of genes to another individual e.g. pea plant might have alleles of height gene to be tall or dwarf

Answer 23

environment can also affect characteristics of an organism e.g. pea plant in sun will gain more sunlight, able to photosynthesise more than pea plant in shade, therefore grow more and taller

Answer 24

usually both genetic and environmental factors contribute to the variation found in individuals of species

Answer 25

continuous: e.g. height, eye colour, skin colour no set categories, is overlap characteristic/phenotype must come from few different genes (polygenic) discontinuous: e.g. blood type, earlobe/ tongue rolling distinct categories with no overlap characteristics must be coded for by 1 gene

Answer 26

continuous variation

Answer 27

a rare, random change in sequence of bases in DNA - can be inherited

Answer 28

sequence of amino acids in the protein - will normally alter shape and function of the protein

Answer 29

replacement of a single base pair with a different pair, or an addition or deletion of one or more base pairs

Answer 30

cell gains an extra chromosome (downs syndrome) or one part of chromosome stuck onto another

Answer 31

neutral (have no effect), but can less often be either positive (increase variation, may be beneficial if environment changes) or negative (protein fails to work properly)

Answer 32

will affect all cells in individual which develops from gamete. means mutation is inherited

Answer 33

will affect only those cells produced by mitosis from the affected cell this type of mutation not inherited

Answer 34

chemicals which cause more frequent mutations e.g. chemicals in tabacco - carcinogens

Answer 35

exposure to ionising radiation e.g. gamma rays, x-rays and ultraviolet light and some chemical mutagens

Answer 36

genetic variation in population e.g. blue eyes are a mutation

Answer 37

Mutations cause variation Rare and random mutation give an organism an advantage E.g. camouflage, able to get more food, escape predators This individual survives longer and reproduces more passed on advantageous allele to offspring happens over many generations

Answer 38

rare and random mutation cause variation variation makes bacteria resistant, causing it to survive and reproduce more, passing advantageous allele to offspring. Happens by natural selection and over many generations Increase bacterial population can lead to infections being difficult to control

Answer 39

insertion of base or deletion: every codon after mutation is different: frameshift

3 Inheritance Flashcards

(66 cards)