Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

AQA Biology > Inheritance > Flashcards

Inheritance Flashcards

You may prefer our related Brainscape-certified flashcards:
AP® Biology flashcards Biology 101 flashcards
1
Q

Meiosis vs mitosis

A
  • meiosis leads to non-identical cells
    being formed
  • mitosis leads to identical cells being formed
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Sexual vs asexual reproduction

A

sexual
- involves the joining (fusion) of male and female gametes:
* sperm and egg cells in animals
* pollen and egg cells in flowering plants
- mixing of genetic information=variety in the offspring
- formation of gametes involves meiosis

Asexual
- only one parent and no fusion of gametes
- no mixing of genetic information
- genetically identical offspring (clones)
- Only mitosis is involved

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

cell division: meiosis

A

a cell divides to form gametes
- it copies its genetic information (chromosomes make identical copies of themselves)
- similar chromosomes pair up
- sections of DNA get swapped=cross-over=variation
- pairs of chromosomes divide
- cell divides in 2 and then the 2 cells divide again=4 gametes each with a single set of chromosomes
- all gametes are genetically different from each other

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

when do gametes join?

A
  • gametes join at fertilisation to restore the normal number of chromosomes
  • new cell divides by mitosis=number of cells increases
  • as the embryo develops cells differentiate
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

pros and cons of sexual reproduction

A

pros
* produces variation in the offspring=if the environment changes variation gives a survival advantage by natural
selection which can be speeded up by humans in selective breeding to
increase food production

cons
- takes time and energy to find mates
- difficult for isolated members of the species to reproduce

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

pros and cons of asexual reproduction

A

pros
- only one parent needed
- more time and energy efficient as do not need to find a mate
- faster than sexual reproduction
- many identical offspring can be produced when conditions are favourable

cons
- limited genetic variation in population (all offspring is genetically identical to their parent)
- population is vulnerable to changes in the conditions and may be only suited for one habitat
- disease is likely to affect the whole population as there’s no genetic variation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

how do organisms reproduce?

A
  • Malarial parasites reproduce asexually in the human host, but sexually in the mosquito
  • Many fungi reproduce asexually by spores but also reproduce sexually to
    give variation.
  • Many plants produce seeds sexually, but also reproduce asexually by runners such as strawberry plants, or bulb division such as daffodils
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what is DNA and where is it found?

A
  • a polymer made up of 2 strands to form a double helix shape
  • in the nucleus’ genetic material, contained in chromosomes
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what is a gene?

A

a small section of DNA on a chromosome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

what does a gene code for?

A

a particular sequence of amino acids, to make a specific protein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what is a genome?

A

the entire genetic material of that organism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

why is the human genome project important?

A
  • allows scientists to identify genes that are linked to different types of diseases=develop effective treatments
  • trace migrations of certain populations of people around the world
  • gives us an understanding of inherited disorders and can help develop treatments
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what is DNA?

A

a polymer made of repeating nucleotide units different nucleotides

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what is a nucleotide made of?

A
  • a sugar and
    phosphate group=backbone which alternate
  • one of four different bases attached to the sugar
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what are the 4 bases and how do they pair up?

A
  • A (adenine)
  • C (cytosine)
  • G (guanine)
  • T (thymine)
  • a+t & c+g pair together=complimentary base pairing
  • joined by weak hydrogen bonds
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what do 3 bases code for?

A

an amino acid
- order of bases control the order in which amino acids are assembled to form a protein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

structure of DNA

A

double-helix

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

protein synthesis

A

transcription - copying of DNA
- DNA molecule is unzipped around the gene
- DNA is a double stranded molecule so it needs to be unzipped to expose one strand
- single strand of DNA acts as a template
- RNA polymerase helps make a copy of DNA as mRNA
- RNA polymerase binds to the non-coding region in front of a gene on one of the DNA strands and uses free nucleotides to produce a complementary mRNA strand of the coding part of the gene

Translation
- mRNA leaves the nucleus, moves into the cytoplasm and attaches to the ribosome
- tRNA molecules complementary to the mRNA arrive at the ribosome
- when the mRNA moves to the ribosome, it recruits tRNA that are complementary to the base sequence of the mRNA
- the tRNA has an anti-codon that is complementary to the mRNA’s codon
- the tRNA molecule carry amino acids with it
- the bases on the mRNA are read in threes and code for a specific amino acid
- the amino acids then bond with another and polypeptides are formed
- a polypeptide chain is formed and released and then folds in a specific shape to make a protein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

why is the shape of a protein important?

A

the unique shape enables the proteins to do their job

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

types of protein

A

enzymes - biological catalysts
hormones - used to carry messages around the body
structural eg. collagen (strengthens connective tissues eg. ligaments or cartilage) - physically strong

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

How does the structure of DNA affect protein synthesis?

A

it determines the sequence of nucleotides, which determine the sequence of amino acids in proteins
- during protein synthesis, DNA is transcribed into RNA, which is then translated into proteins based on the sequence of nucleotides
- any changes in the DNA sequence can alter the resulting protein and potentially affect its function

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

how does variation of the coding parts of DNA affect the phenotype

A
  • a strand of DNA is organised into sections of coding DNA (genes), separated by sections of the non-coding DNA
  • if a mutation happens=DNA bases may be changed, added, or deleted=changes the sequence of bases, so the order of bases in mRNA produced during transcription may be different
  • the amino acid may be assembled in a different order=wrong protein produced, or it may fold incorrectly and form a different shape eg. if the protein is an enzyme, it’s active site may change shape=no longer be able to bind to its substrate and catalyse a specific chemical reaction
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

how does variation in the non-coding parts [switch genes on and off=control if they’re expressed or not (used to make a protein)] of DNA affect the phenotype

A
  • there are specific sequences of DNA bases found before a gene which trigger the process of transcription which are found in the non-coding sections of DNA
  • if a mutation occurs in this sequence, the gene may not be transcribed into the mRNA=protein the gene codes for will not be produced
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what is a mutation?

A

random change in an organism’s DNA and can be inherited

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

when do mutations occur?

A

continuously
- most do not alter the protein, or only alter it slightly so that its appearance or function is not changed
- few mutations code for an altered protein with a different
shape eg. enzyme may no longer fit the substrate binding site or a structural protein may lose its strength
- if there’s a mutation in the non-coding part of DNA, it alters how genes are expressed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

types of mutations

A
  • insertions - a new base is inserted into the DNA sequence where it shouldn’t be & has a knock-on effect on bases further down
  • deletions - a random base is deleted from the DNA sequence & has a knock-on effect on bases further down
  • substitutions - a random base in the DNA sequence is changed to a different base
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

what is a gamete?

A

a sex cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

what is a chromosome?

A

a molecule made up of many coiled up sections of DNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

what is an allele?

A

different forms of the same gene

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

what is a dominant allele?

A

more powerful allele
always expressed
represented by an uppercase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
31
Q

what is a recessive allele?

A

less powerful allele
only expressed if there’s two of them therefore no dominant allele
represented by a lowercase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
32
Q

what is a homozygous?

A

both of the same allele
can be either homozygous dominant or homozygous recessive

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
33
Q

what is heterozygous?

A

having two different alleles

34
Q

what is a genotype?

A

he genetic makeup of an individual, which determines their specific traits and characteristics

35
Q

what is a phenotype?

A

observable physical characteristics and traits of an individual that are determined by their genotype and the environment

36
Q

what characteristics are controlled by a single gene?

A

fur colour in mice
red-green colour blindness in humans
however most characteristics are a result of multiple genes interacting, rather
than a single gene

37
Q

Polydactyly (having extra fingers or toes)

A
  • caused by a dominant allele
  • not life-threatening
  • can be inherited by only one allele from one parent
38
Q

Cystic fibrosis (a disorder of cell membranes)

A
  • caused by a recessive allele
  • body produces a lot of sticky mucus in the air passages and in the pancreas
  • the allele is carried by about 1 in 25 people
  • one copy of allele=carrier
39
Q

what is embryonic screening?

A
  • in IVF, a cell can be removed from each embryo to analyse its genes before being implanted
40
Q

what are the problems regarding embryonic screening?

A
  • controversial
  • for embryos produced by IVF - the bad alleles would be destroyed after screening
  • for embryos in the womb - screening could lead to the decision to terminate the pregnancy
  • very expensive, however the cost of the healthcare for the child who suffers from a disorder may be much greater
  • a false positive or a false negative result=lead to great trauma to a family
41
Q

arguments for and against embryonic screening

A

for
- help stop people suffering
- treating disorders costs the gov and taxpayers a lot of money
- laws to stop it going too far eg. parents can’t select the sex of their baby

against
- implies that people with genetic problems are undesirable=increases prejudice
- may come to a point where everyone wants the most desirable one eg. they want a blue-eyed, smart, blond boy
- expensive

42
Q

how many chromosome are the in a body cell?

A

23 pairs

43
Q

how many pairs determine what?

A

22 pairs determine characteristics
1 pair carries genes that determine sex

44
Q

female and male chromosomes

A

female - XX=allow female characteristics to develop
male - XY=Y allows male characteristics to develop

45
Q

how does the genome affect the development of a phenotype in an organism?

A
  • characteristics of an organism are determined by the genes inherited by their parents
  • genes are passed on in gametes from which the offspring develop
  • most animals/plants inherit genes from both parents=combination of the parents’ genes=genetic variation=no two of the species are genetically identical apart from identical twins
46
Q

what characteristics are determined by genes only?

A

in plants
- flower colour
in animals
- eye colour
- blood group
- inherited disorders eg. cystic fibrosis

47
Q

how does the environment influence the development of a phenotype in an organism?

A
  • can cause differences between members of the same species depending on the conditions that organisms live and grow=environmental variation
48
Q

what characteristics are influenced by the environment?

A
  • how green leaves are=depends on light
  • getting a suntan
49
Q

what is variation?

A

differences in the characteristics of individuals in a population

50
Q

what is variation caused by?

A
  • inherited genes=genetic cause
  • conditions in which they have developed=environmental causes
  • a combination of genes and the environment
51
Q

what are most of our characteristics caused by?

A

genes and environment
eg. skin colour, body weight, height etc

52
Q

how does variation happen?

A

due to mutations as they change the sequence of bases in DNA
- most have no effect on the phenotype
- some influence phenotype
- very few determine phenotype (result in a new phenotype)
if the new phenotype is better suited to the environment, it can lead to rapid change in the species

53
Q

what is evolution?

A

a change in the inherited characteristics of a population over time through a process of
natural selection which may result in the formation of a new species

54
Q

what is the theory of evolution?
(natural selection)

A

all species of living things have evolved from simple life forms that first developed more than three billion years ago

55
Q

Darwin’s theory

A
  • organisms in a species show a wide variation in their characteristics and compete for limited resources in an ecosystem
  • he concluded that the organisms with the most suitable characteristics for the environment would be more successful competitors and would be more likely to survive=’survival of the fittest’
  • organisms that survive=more likely to reproduce and pass on the genes for the advantageous characteristics to their offspring, opposite for less well adapted organisms
  • over time, beneficial characteristics become more common in the population and the species changes=evolution
56
Q

why was the theory gradually accepted?

A
  • the theory challenged the idea that God made all the animals and plants that live on Earth
  • there was insufficient evidence at the time the theory was published to convince many scientists
  • the mechanism of inheritance and variation was not known until 50 years after the theory was published
57
Q

Jean-Baptiste Lamarck’s theory

A
  • the changes an organism acquires during its lifetime will be passed onto its offspring
  • however we now know that in the vast majority of cases this type of inheritance cannot occur
58
Q

Mendel’s work

A
  • mid-19th century Gregor Mendel carried out breeding experiments on pea plants (tall pea plant+dawrf pea plants=off spring were all tall; bred two of the tall pea plants=3 tall plants+1 dwarf plant; this showed that the unit for tall plants was dominant, T, over the unit for dwarf plants, t)
  • his observations:
    characteristics in plants are determined by hereditary units
    hereditary units passed onto offspring are unchanged from both parents, one from each
    hereditary units can be dominant or recessive
59
Q

why was Mendel’s work not accepted until he died?

A
  • late 19th century behaviour of chromosomes during cell division was observed
  • early 20th century it was observed that chromosomes and Mendel’s ‘units’ behaved in similar ways=led to the idea that the ‘units’, now called genes, were located on chromosomes
  • in 1953, the structure of DNA was determined and the
    mechanism of gene function worked out
  • this scientific work by many scientists led to the gene theory being developed
60
Q

evidence for the theory of evolution

A
  • evidence for Darwin’s theory is now available as it has been shown that characteristics are passed on to offspring in genes
  • further evidence in the fossil record and the knowledge of how resistance to antibiotics evolves in bacteria
61
Q

resistant bacteria

A
  • bacteria evolve rapidly because they reproduce at a fast rate
  • mutations of bacteria=new strains=some resistant strains=x killed by antibiotic=survive and
    reproduce=population of the resistant strain rises=resistant
    strain will then spread because people are not immune to it and there is no effective treatment.
    eg. MRSA is resistant to antibiotics
  • To reduce the rate of development of antibiotic resistant strains:
  • doctors should not prescribe antibiotics inappropriately
  • patients should complete their course of antibiotics=all bacteria are killed and none survive to mutate and form resistant strains
  • the agricultural use of antibiotics should be restricted.
  • development of new antibiotics is costly and slow=unlikely to
    keep up with the emergence of new resistant strains
62
Q

what are fossils?

A

the ‘remains’ of organisms from millions of years ago, which
are found in rocks

63
Q

how are fossils formed?

A
  • from parts of organisms that haven’t decayed because one or more of the conditions needed for decay are absent eg. in amber+tar pits=x oxygen or moisture=decay microbes x survive, in glaciers=too cold for decay microbes to work, in peat bogs=too acidic=peat bog man
  • when parts of the organism are replaced by minerals as they decay (most happen this way) –> things like teeth, bones, shells=x decay easily=last a long time when buried=eventually replaced by minerals as they decay=form a rock-like substance shaped like the original hard type, surrounding sediments also turn into rock but fossil stays distinct
  • as preserved traces of organisms, such as footprints, burrows and rootlet traces –> organism is buried in soft material eg. clay=hardens around it+organism decays=leaving a cast of itself=burrows and rootlet traces (roots), footprints can be pressed into these materials when soft=leaves an impression when hardened
64
Q

what can we learn from fossils?

A

how much or how little different organisms have changed as life developed on Earth

65
Q

why can’t we be sure of how life began?

A

Many early forms of life were soft-bodied, which means that they have left few traces behind or the traces there were have been mainly destroyed by geological activity=incomplete fossil record

66
Q

how scientific methods and theories develop over time

A
  • there are various hypotheses suggesting how life first began but no on really knows
  • maybe the first life forms came into existence in a primordial swamp/under the sea or simple organic molecules were brought to earth by comets=become more complex molecules=eventually simple life forms
  • these hypotheses can’t be supported or disproved due to a lack of good+solid evidence=incomplete fossil record
67
Q

when does extinction occur?

A

when there are no remaining individuals of a species still alive

68
Q

what factors contribute to extinction?

A
  • environment changes too quickly
  • a new predator kills them all
  • a new disease kills them all
  • can’t compete with another (new) species for food
  • catastrophic event happens that kills them all eg. volcanic eruption, collision with an asteroid
69
Q

what is a species?

A

a group of similar organisms that can reproduce to give fertile offspring

70
Q

what is speciation?

A

development of a new species

71
Q

when does speciation occur?

A

the populations become extremely varied and successful interbreeding cannot happen anymore

72
Q

how does speciation occur?

A

isolation and natural selection
- isolation is where populations of a species are separated due to a physical barrier eg. a river, earthquake=geographically isolated
- conditions on both sides of the barrier are slightly different eg. different climates=different environments on each side=different characteristics will become more common in each population due to natural selection=each population shows genetic variation because they have a wide range of alleles
- in each population=individuals with characteristics that make them better adapted to their environment=better chance of survival=more likely to breed successfully=alleles that control the beneficial characteristics are more likely to be passed on to the next generation
- eventually, individuals from the different populations will have changed so much that they won’t be able to breed to produce fertile offspring=two different species

73
Q

Alfred Russel Wallace’s theory

A
  • Wallace independently proposed the theory of evolution by natural selection
  • He published joint writings with Darwin in 1858 which prompted Darwin to publish On the Origin of Species (1859) the following year
  • Wallace worked worldwide gathering evidence for evolutionary theory
  • He is best known for his work on warning colouration in animals and his theory of speciation
  • Wallace did much pioneering work on speciation but more evidence over time has led to our current understanding of the theory of speciation
74
Q

genetic engineering

A
  • a process which involves modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic
    1.Enzymes are used to isolate (cut out) the required gene
    2. This gene is inserted into a vector
    3. The vector is usually a bacterial plasmid or a virus
    4. The vector is used to insert the gene into the required cells of the target organism
    5. Genes are transferred to the cells of animals, plants or microorganisms at an early stage in their development so that they develop with desired characteristics
  • it has been done by with bacteria which was genetically modified to produce human insulin, GM crops eg. to improve the size or quality of fruit, make them resistant to disease, insects, etc; sheep have been genetically engineered to produce substances eg. drugs in their milk, gene therapy (genetic modification treatment for inherited diseases eg. inserting working genes into people with disease)
75
Q

pros and cons of genetic engineering

A

pros
- chosen characteristics for GM crops=increase yields=more food
- people living in developing countries lack nutrients in their diet=GM crops engineered to contain the nutrient they’re missing eg. golden rice=has beta-carotene=lack of this causes blindness

cons
- worries about the long-term effects=may create unwanted problems accidently=passed on to future generations
- affect the number of wild flowers/insects=reducing biodiversity
- not everyone is convinced they’re safe and some are concerned we may become allergic to it (but there’s probably no more risk than normal food)
- transplanted genes may get out into the natural environment eg. herbicide resistance gene may be picked up by weeds=superweed created

76
Q

selective breeding/artificial selection

A
  • humans breed plants and animals for particular genetic characteristics
  • humans have been doing this for thousands of years since they first bred food crops from wild plants and domesticated animals
    1. choosing parents with the desired characteristic from a mixed population
    2. breed them together=offspring
    3. choose off spring with desired characteristics
    4. from the offspring those with the desired characteristic are bred together
    5. this continues over many generations until all the offspring show the desired
    characteristic
    The characteristic can be chosen for usefulness or appearance eg.
  • disease resistance in food crops
  • animals that produce more meat or milk
  • Domestic dogs with a gentle nature
  • large or unusual flowers
77
Q

problems with selective breeding

A
  • can lead to ‘inbreeding’ or reduction of gene pool (number of different alleles in a population)=some breeds are particularly prone to disease or inherited defects=less chance of any resistant alleles in the population
78
Q

plant cloning

A

Tissue culture
- a few plants cells are put in a growth medium with hormones=grow into clones of the parent
- new plants are made very quickly, in very little space and grown all year
- important for preserving rare plant species or commercially in nurseries.

Cuttings
- gardeners take cutting from good parent plants++plant them to produce genetically identical plants
- produced quickly and cheap
- an older and simpler than tissue culture

79
Q

animal cloning

A

Embryo transplants
Egg cells from the best cow areartificially fertilisedusing sperm cells taken from the best bull
This forms anembryo
The developing animal embryo is thensplit apart many timesbefore the cells of the embryo become specialised
This formsmany separate embryos that are genetically identical
These cloned embryos are thentransplanted into host mothers
The calves born from these host mothers are all genetically identical

Adult cell cloning
- nucleus is removed from an unfertilised egg cell
- nucleus from an adult body cell is inserted into the egg cell
- an electric shock stimulates the egg cell to divide to form an embryo
- these embryo cells contain the same genetic information as the adult body cell
- When the embryo has developed into a ball of cells, it is inserted into the womb of an adult female to continue its development=grows into a clone of the original adult body cell
eg. Dolly the sheep

80
Q

pros and cons of cloning

A

pros
- quickly gets you ideal offspring
- study of animal clones lead to greater understanding of the development of an embryo, ageing and age-related disorders
- help preserve endangered species

cons
- reduced gene pool=can be all wiped out by a disease
- cloned animals may not be as healthy as normal ones eg. Dolly the sheep had arthritis
- some people worry that humans may be cloned in the future=if allowed, any success may follow many unsuccessful attempts eg. born severely disabled

81
Q

classification of organisms

A
  • traditionally living things have been classified into groups depending on their structure and characteristics in a system developed by Carl Linnaeus
  • Linnaeus classified living things into:
    kingdom
    phylum
    class
    order
    family
    genus
    species
  • organisms are named by the binomial system of genus and species eg. homo sapiens= homo is genus & sapiens is species=avoids confusion as it’s used worldwide
  • as evidence of internal structures became more developed due to improvements in microscopes, and the understanding of biochemical
    processes progressed, new models of classification were proposed
  • due to evidence available from chemical analysis there is now a ‘threedomain system’ developed by Carl Woese. In this system organisms are divided into:
  • archaea (primitive bacteria usually living in extreme environments)
  • bacteria (true bacteria)
  • eukaryota (which includes protists, fungi, plants and animals)
82
Q

evolutionary trees

A
  • a method used by scientists to show how they believe organisms are related=show common ancestors and relationships between species
  • more recent common ancestor=more closely related=more characteristics shared
  • they use current classification data for living organisms and fossil data for extinct organisms

AQA Biology (7 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions