November mock prep- topic 4

Question 1

gene

Answer 1

section of DNA that codes for a specific sequence of amino acids, making a polypeptide

Question 2

locus

Answer 2

specific location of a gene on a chromosome

Question 3

what are the 3 characteristics of the genetic code?

Answer 3

universal-
same for multiple organisms

non-overlapping-
each base sequence only read once

degenerate-
amino acids coded for by multiple triplets

Question 4

what is the same at the start of every DNA sequence?

Answer 4

the start codon

Question 5

what marks the end of the DNA sequence?

Answer 5

the stop codon

Question 6

what are introns?

Answer 6

non-coding sequences found in a gene

Question 7

what are exons?

Answer 7

coding sequences within a gene

Question 8

when are chromosomes visible?

Answer 8

when a cell is dividing

Question 9

what are chromatids?

Answer 9

one of the two strands that make up a chromosome joined at the centromere

Question 10

how are chromosomes formed?

Answer 10

DNA combines with histone forming a DNA-histone complex

coils then folds to form loops

loops coil and pack together to form the chromosome

Question 11

what is a homologous pair?

Answer 11

one chromosome from maternal chromosomes and one chromosome from paternal chromosomes

Question 12

what is an allele?

Answer 12

alternative form of a gene

Question 13

what happens when the base sequence of a gene changes?

Answer 13

a new allele is produced due to the mutation

this codes for a different amino acid creating a different polypeptide

this therefore creates a different protein

Question 14

what is a codon?

Answer 14

sequence of 3 bases on mRNA

Question 15

what is the genome?

Answer 15

complete set of genes in a cell

Question 16

what is the proteome?

Answer 16

full range of proteins produced by the genome

Question 17

what is the structure of RNA?

Answer 17

ribose sugar
phosphate group
bases- A-U/ C-G

Question 18

mRNA

Answer 18

single helix
long strand
transcription
leaves through nuclear pores
acts as template for protein synthesis
information in form of codon

Question 19

tRNA

Answer 19

small
around 80 nucleotides
anticodon on opposite end- specific to the amino acid
clover leaf shape with one end extended past the other where the amino acid attaches

Question 20

describe transcription

Answer 20

process of making pre-mRNA

DNA helicase breaks hydrogen bonds exposing the nucleotides in that area, creating a template strand

bases on template strand pair with complementary RNA nucleotides using RNA polymerase

RNA polymerase reaches stop codon and detaches

Question 21

describe splicing

Answer 21

process of making mRNA

introns removed as they are non coding and would prevent protein synthesis

functional exons are joined

Question 22

describe translation

Answer 22

1) mRNA leaves through nuclear pore into cytoplasm
2) ribosome attaches to start codon
3) tRNA with complementary anticodon pairs up with codon, carrying a specific amino acid
4) tRNA binds with next codon carrying a different amino acid
5) ribosome moves along mRNA bringing two tRNA molecules each time with amino acids being joined by peptide bonds
6) first tRNA is released when ribosome moves to third codon so it can collect another amino acid
7) process continues until stop codon is reached

Question 23

what is a mutation?

Answer 23

any change to the quantity or base sequence of the DNA

Question 24

what are the 3 mutations?

Answer 24

substitutions-
nucleotide replaced by a different one
usually coding for a new amino acid
this doesn’t always happen due to the genetic code being degenerate

deletion-
nucleotide is lost causing a frame shift often completely changing the amino acid sequence

addition-
new nucleotide is added causing a frameshift

Question 25

what are the two chromosome mutations?

Answer 25

polyploidy- change in whole set of chromosomes non-disjunction- changes in the number of individual chromosomes when chromosomes fail to separate leads to gamete having one more or one less chromosome

Question 26

why is meiosis important?

Answer 26

for sexual reproduction if each gamete was diploid, the cell would produce 92 chromosomes to maintain a constant number they must be halved at some point

Question 27

how many daughter cells does meiosis produce?

Answer 27

4 daughter cells (haploid)

Question 28

describe meiosis

Answer 28

first division: 1) homologous chromosomes pair up and chromatids wrap around each other 2) equivalent portions can be exchanged during crossing over 3) divides with one chromosome from each pair going into one daughter cell second division: 1) chromatids move apart 2) 2 daughter cells divide to produce 4 daughter cells

Question 29

how does meiosis produce genetic variation?

Answer 29

independent segregation of homologous chromosomes new combinations of alleles by crossing over

Question 30

what is independent segregation?

Answer 30

one of each chromosome pair will go into one of the daughter cells depends on how they are lined up to which daughter cell they go in

Question 31

describe crossing over

Answer 31

chromatids of each pair become twisted creating tension, breaking a portion of the chromatids

Question 32

describe recombination

Answer 32

rejoin with chromatids of its homologous partner

Question 33

what is genetic diversity?

Answer 33

total number of different alleles in a population

Question 34

what is a population?

Answer 34

group of individuals of the same species that can reproduce to make fertile offspring

Question 35

what does genetic diversity enable?

Answer 35

natural selection to occur

Question 36

when is genetic diversity greater?

Answer 36

with more different alleles wider range of characteristics more likely some individuals will survive environmental change

Question 37

describe natural selection

Answer 37

1) random mutation of alleles within gene pool may result in a new allele 2) this may give the possessor an advantage 3) they will have better chance of breeding successfully and producing more offspring 4) this passes the advantageous allele on to the next generation 5) over time the frequency of the allele increases

Question 38

what is selection?

Answer 38

process by which organisms better adapted to their environment tend to survive and breed

Question 39

directional selection

Answer 39

more extreme phenotypes selected for

Question 40

stabilising selection

Answer 40

favour average individuals- normal phenotype selected for

Question 41

what are the 3 adaptations?

Answer 41

anatomical physiological behavioural

Question 42

what is courtship behaviour?

Answer 42

individuals can identify other members of their own species by how they act identify a mate capable of breeding form a pair bond synchronise mating become able to breed

Question 43

classification

Answer 43

grouping of organisms

Question 44

taxonomy

Answer 44

theory and practice of biological classification

Question 45

artificial classification

Answer 45

divides organisms according to differences that are useful at the time

Question 46

phylogenetic classification

Answer 46

based upon evolutionary relationships classifies species into groups using shared features arranges groups into hierarchy

Question 47

taxon

Answer 47

each group in a phylogenetic biological classification

Question 48

what are the taxons in the phylogenetic classification?

Answer 48

Domain Kingdom Phylum Class Order Family Genus Species mnemonic: do keep ponds clean or frogs get sick

Question 49

what is a phylogeny?

Answer 49

evolutionary relationship between organisms represented by a phylogenetic tree

Question 50

what is biodiversity?

Answer 50

variety of different species in an ecosystem

Question 51

species diversity

Answer 51

number of different species and individuals within a community

Question 52

genetic diversity

Answer 52

variety of genes possessed by the individual

Question 53

ecosystem diversity

Answer 53

range of different habitats

Question 54

species richness

Answer 54

measure of species diversity

Question 55

index of diversity

Answer 55

sum of total no. of organisms of all species/ sum of total no. of organisms of each species

Question 56

impact of agriculture

Answer 56

agricultural ecosystems controlled by humans genetic variety of alleles reduced as farmers select species for specific qualities

Question 57

practices removing habitats

Answer 57

removal of hedgerow/ woodland/ ponds overgrazing creating monocultures

Question 58

practices of farming with an indirect effect

Answer 58

use of pesticides escape if effluent lack of crop rotation

Question 59

conservation techniques

Answer 59

maintain hedgerows plant hedges as field boundaries create ponds leave wet corners of fields organic fertilisers