Genetic info+Variation

Question 1

gene

Answer 1

section of DNA that codes for the sequence of amino acids in a polypeptide and functional RNA

Question 2

eukaryotic DNA vs prokaryotic DNA

Answer 2

eukaryotic-long, linear, histones

prokaryotic (mitochondria+chloroplasts)-short, circular, no histones

Question 3

what does a gene code for

Answer 3

amino acid sequence of polypeptide, a functional RNA

Question 4

what is a locus

Answer 4

location of the gene on the strand of DNA

Question 5

3 properties of genetic code

Answer 5

universal, non overlapping, degenerate

Question 6

Introns vs Exons

Answer 6

Introns-non coding multiple repeats of bases ( removed via splicing before being read)
Exons-coding bases

Question 7

histone

Answer 7

stabilising protein in chromosomes

Question 8

centromere

Answer 8

protein that connects 2 chromatids

Question 9

haploid vs diploid

Answer 9

haploid-eg sperm, egg has 23 chromosomes

diploid-eg normal cell has 23 chromosome pairs

Question 10

what are nucleic acids

Answer 10

eg RNA, DNA

made up of pentose sugar, phosphate group, nitrogenous base

Question 11

allele

Answer 11

code for slightly different versions of the same polypeptide

Question 12

homologous pair

Answer 12

corresponding pairs of chromosomes that are the same size and posses the same genes and centromere position

Question 13

tRNA structure key features

Answer 13

attachment point of amino acids
H bonds between base pairs
anti-codon loop
(clover shape)

Question 14

the role of RNA

Answer 14

transcription and translation

Question 15

DNA vs RNA

Answer 15

DNA:
double stranded helix, longer, deoxyribose, ATCG
RNA:
single stranded helix, shorter, ribose, AUCG

Question 16

mRNA structure key features+ purpose

Answer 16

linear shape, proteins made in cytoplasm as DNA is too large to exit nucleus RNA transcribes it and carries info out via nuclear pores

Question 17

RNA transcription steps

Answer 17

1-RNA polymerase attaches to the DNA-
H bonds break, uncoil+ expose bases,1 strand used as template
2-complementary mRNA formed-
free RNA nucleotides line up along exposed bases
3-RNA polymerase moves down DNA strand-
mRNA strand assembled, H bonds reform+ re coil once polymerase has passed
4-RNA polymerase reaches stop signal-

Question 18

enzyme used in transcription

Answer 18

RNA polymerase

Question 19

pre-mRNA vs mRNA

Answer 19

pre-mRNA=eukaryotes as they contain introns
mRNA=prokaryotes as they don’t contain introns

introns removed via splicing and exons are joined together to form mRNA

Question 20

RNA translation

Answer 20

1-mRNA attaches to ribosome+ tRNA mols carry amino acids to it
2-complementary tRNA attaches to mRNA
3-2 amino acids joined by peptide bond (empty tRNA mol leaves)
4-process continues until stop signal
polypeptide is formed

Question 21

types of mutation

Answer 21

insertion
deletion
substitution

Question 22

what is a mutation

Answer 22

change in DNA base sequence of chromosomes

Question 23

silent mutation

Answer 23

substitution can have no impact on amino acid due to degenerate nature of code
eg sickle cell anaemia

Question 24

mutagenic agents

Answer 24

increases probability of random mutations (DNA being misread in replication)
eg radiation, carcinogens

Question 25

chromosome non-disjunction

Answer 25

failure of chromosomes to separate properly in anaphase or meiosis eg Down’s Syndrome

Question 26

intron mutations

Answer 26

affect what genes are turned on or off

Question 27

meiosis steps

Answer 27

1-DNA unravels+ replicates
2-DNA condenses
3-homologous pairs line up
4-crossing over (recombinant chromosomes)
5-meiosis 1-homologous pairs separate
6-meiosis 2-sister chromatids separate

Question 28

gamete variation due to…

Answer 28

crossing over of chromatids
-each contain chromatids w different alleles
independent segregation
-random chromosome assortment- variation in any offspring

Question 29

meiosis vs mitosis

Answer 29

meiosis=
reduce chromosome number, 2 divisions, 4 daughter cells, cross over, genetically unidentical product
mitosis=
maintain chromosome number, 1 division, 2 daughter cells, don’t cross over, genetically identical product