module 4

Question 1

what is dna wrapped around and why

Answer 1

its wrapped around proteins called histones because it is a very long molecule

Question 2

dna in prokaryotes

Answer 2

also carry dna as chromosomes like in eukaryotes but isnt wrapped around histones and is a much shorter molecule which is circular

Question 3

whats a gene

Answer 3

a sequence of dna bases that code for a polypeptide chain

Question 4

how many bases code for an amino acid

Answer 4

3 or 1 triplet

Question 5

whats a genome

Answer 5

the cells genome is the complete set of genes in the cell

Question 6

whats a proteome

Answer 6

a cells proteome is the full range of proteins that the cell is able to produce

Question 7

introns

Answer 7

sectons of genes that do not code for amino acids

Question 8

allele

Answer 8

a different variation of a gene

Question 9

whats a locus

Answer 9

a fixed position on a chromosome

Question 10

what bases do rna molecules contain

Answer 10

a u , g c

Question 11

whats mRNA

Answer 11

made during transcription. it carries the genetic code from the DNA to the ribosomes. it is a single polynucleotide strand. 3 bases are called a codon not a triplet like in DNA

Question 12

whats tRNA

Answer 12

transfer RNA is involved in translation , it carries the amino acids that are used to make proteins to the ribosomes. its a single stranded chain thats folded into a clover shape. every tnra molecule has a specific sequence of 3 bases at one end called an anticodon, they also have an amino acid binding site on the other end

Question 13

transcription process

Answer 13

hydrogen bonds break between strands of DNA ( DNA helicase)
one strand of DNA acts as a template
free RNA nucleotides now align by complimentary base pairings
uracil instead of thymine
RNA polymerase creates phosphodiester bonds between these RNA nucleotides
splicing then occurs and the mrna moves out the nuclear envelope

Question 14

translation

Answer 14

occurs in the cytoplasm
mRNA attaches to ribosomes on the rough endoplasmic reticulum.
the anticodons on the tRNA molecule bind to their complimentary mRNA codon.
tRNA brings specific amino acid
these amino acids then join together via a peptide bond with the use of ATP. the ribosome then moves along the mRNA to form a polypeptide chain

Question 15

what does non-overlapping mean

Answer 15

base triplets dont share their bases

Question 16

what does degenerate mean

Answer 16

there are more possible combinations of triplets than there are amino acids. some amino acids are coded for by more than 1 base triplet

Question 17

start and stop codons

Answer 17

they are found at the start and end of the mRNA and they tell the cell when to start and stop production of the protein

Question 18

what does in mean when saying the genetic code is universal

Answer 18

the same specific base triplets code for the same amino acids in all living things

Question 19

whats a zygote

Answer 19

when sperm fertilises an egg a zygote is formed

Question 20

diploid

Answer 20

cell containing 2 copies of each chromosome, one from the mother and one from the farther

Question 21

haploid

Answer 21

theres only 1 copy of each chromosome

Question 22

where does meiosis take place

Answer 22

in reproductive organs

Question 23

meiosis process

Answer 23

replication- so now theres 2 copies of each chromosomes, called chromatids
DNA then condenses to form double-armed chromosomes each made from 2 sister chromatids
cell then divides
then divides again and the pairs of sister chromatids are separated
4 haploid cells that are gametes and are genetically different are produced

Question 24

chromatid crossing over in meiosis division 1

Answer 24

the chromatids twist around each other and bits of chromatids swap over. the chromatids still contain the same genes but now have a different combinations of alleles

Question 25

independent segregation of chromosomes

Answer 25

when the homologous chromosomes are separated in meisosis 1 its completely random which chromosome from each pair ends up in which of the 4 daughter cells this can lead to genetic variation in any potential offspring

Question 26

what increases the rate of mutation

Answer 26

mutagenic agents. mutations occur spontaneously, but some things can increase the rate at which the occur eg uv light, ionising radiation, asbestos

Question 27

whats genetic diversity

Answer 27

the number of different alleles of genes in a species or population

Question 28

how is genetic diversity increased within a population

Answer 28

mutations in the DNA forming new alleles. different alleles being introduced into a population when individuals from another population migrate into them and reproduce ( also known as gene flow )

Question 29

how does a genetic bottleneck reduce genetic diversity

Answer 29

a genetic bottleneck is an event that causes a big reduction in a population, this reduces the number of different alleles in the gene pool and so reducing genetic diversity. the survivors reproduce and a larger population is created from a few individuals

Question 30

whats the founder affect

Answer 30

describes what happens when just a few organisms from a population start a new colony and there are only a small number of different alleles in the initial gene pool

Question 31

natural selection

Answer 31

individuals that have an advantageous allele that increases their survival are more likely to survive an event, reproduce and pass on their genes. this means in the next generation their will be a higher proportion of the organism with the advantageous allele, over generations this can lead to evolution

Question 32

whats a behavioural adaptation

Answer 32

ways an organism acts that increases its chance of survival and reproduction eg playing dead

Question 33

whats a physiological adaptation

Answer 33

processes inside an organism body that increases the chance of survival eg bears hibernate over the winter and conserve energy so they dont need to look for food in the months where its scarce

Question 34

whats a anatomical adaptation

Answer 34

structural features of an organisms body that increases its chance of survival. eg whales have a thick layer of blubber which helps them keep warm in the cold sea

Question 35

what is directional selection

Answer 35

where individuals with alleles for characteristics of an extreme type are more likely to survive and reproduce. the mean shifts towards this new extreme type

Question 36

whats the inhibition zone

Answer 36

a clear patch in the lawn of bacteria, the larger the zone the more bacteria was inhibited from growing

Question 37

test for the antibiotics using agar plates

Answer 37

use sterile pipette to transfer bacteria to agar plate and spread it. use sterile forceps to place paper discs soaked in different antibiotics spaces apart on the plate incubate at 25degrees for 48hours

Question 38

aseptic techniques to prevent contamination of microbial cultures

Answer 38

regularly disinfect work surfaces work near bunsen burner, hot air rises so any microbes in the air should be drawn away form the culture minimise the time spent with the lid of the agar briefly flame the neck of the glass container of broth just after its opened and before its closed also wash hands regularly