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A-level Biology > module 4 > Flashcards

module 4 Flashcards

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1
Q

what is dna wrapped around and why

A

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

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2
Q

dna in prokaryotes

A

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

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3
Q

whats a gene

A

a sequence of dna bases that code for a polypeptide chain

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4
Q

how many bases code for an amino acid

A

3 or 1 triplet

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5
Q

whats a genome

A

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

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6
Q

whats a proteome

A

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

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7
Q

introns

A

sectons of genes that do not code for amino acids

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8
Q

allele

A

a different variation of a gene

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9
Q

whats a locus

A

a fixed position on a chromosome

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10
Q

what bases do rna molecules contain

A

a u , g c

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11
Q

whats mRNA

A

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

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12
Q

whats tRNA

A

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

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13
Q

transcription process

A

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

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14
Q

translation

A

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

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15
Q

what does non-overlapping mean

A

base triplets dont share their bases

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16
Q

what does degenerate mean

A

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

17
Q

start and stop codons

A

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

18
Q

what does in mean when saying the genetic code is universal

A

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

19
Q

whats a zygote

A

when sperm fertilises an egg a zygote is formed

20
Q

diploid

A

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

21
Q

haploid

A

theres only 1 copy of each chromosome

22
Q

where does meiosis take place

A

in reproductive organs

23
Q

meiosis process

A

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

24
Q

chromatid crossing over in meiosis division 1

A

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

25
Q

independent segregation of chromosomes

A

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

26
Q

what increases the rate of mutation

A

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

27
Q

whats genetic diversity

A

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

28
Q

how is genetic diversity increased within a population

A

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 )

29
Q

how does a genetic bottleneck reduce genetic diversity

A

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

30
Q

whats the founder affect

A

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

31
Q

natural selection

A

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

32
Q

whats a behavioural adaptation

A

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

33
Q

whats a physiological adaptation

A

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

34
Q

whats a anatomical adaptation

A

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

35
Q

what is directional selection

A

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

36
Q

whats the inhibition zone

A

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

37
Q

test for the antibiotics using agar plates

A

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

38
Q

aseptic techniques to prevent contamination of microbial cultures

A

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

A-level Biology (12 decks)

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