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BIOLOGY PAPER 2 > B6 Inheritance, Variation And Evolution > Flashcards

B6 Inheritance, Variation And Evolution Flashcards

1
Q

What is sexual reproduction

A

Joining of male and female gametes

-sperm and egg cells in animals
-pollen and egg in flowering plants

Gametes are formed by meiosis as they are non identical

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2
Q

What is asexual reproduction

A

Involves one parent with no gametes joining

Happens using the process of mitosis where two identical cells are formed from one cell

It leads to clones which are genetically identical to each other and the parent.

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3
Q

What are the stages of meiosis

A

-cell makes copies of its chromosomes so it has double the amount of genetic information
-cell divides into two cells, each with half the amount of chromosomes (46)
-the cell divides again producing four cells, each with a quarter of chromosomes (23)
-these cells are called gametes and they are all genetically different from one another because the chromosomes are shuffled during the process, resulting in random chromosomes ending up in each of the four cells

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4
Q

Advantages of sexual reproduction

A

Produces variation in offspring
-this means if the environment changes, it is likely that an organism in the species will have a characteristic that allows them to survive

It allows us to use selective breeding
-this type of reproduction mixes the genetic information from two organisations
-organisations with different desirable characteristics can breed to produce offspring with even more desirable characteristics
-this speeds up natural selection

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5
Q

What’s the advantages of asexual reproduction

A

-only one parent is needed
-uses less energy and is faster as organisms do not need to find a mate

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6
Q

What is a gene

A

Small section of dna on a chromosome- a triplet of bases that codes for a specific protein- each gene codes for a particular sequence of amino acids, together a chain of amino acids can join to make a protein

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7
Q

What is a genome

A

All the genes coding for all the proteins within an organism

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8
Q

What does DNA stand for

A

Deoxyribonucleic acid

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9
Q

What is dna made up of

A

Nucleotides

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10
Q

What are nucleotides made up of

A

Sugar molecule

Phosphate molecule

Organic base

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11
Q

What are the four bases and which pair with which

A

Adenine
Thymine
Guanine
Cytosine

A and T
C and G

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12
Q

What are non coding dna responsible for

A

Switching genes on and off

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13
Q

What are the stages of protein synthesis

A
  1. DNA contains the genetic code for making a protein, but it cannot move out of the nucleus as it is too big.
  2. The two strands pull apart from each other and mRNA nucleotides match to their complimentary base on the strand.
  3. The mRNA nucleotides themselves are then joined together, creating a new strand called the mRNA strand. This is a template of the original DNA.
  4. The mRNA then moves out of the nucleus to the cytoplasm and onto structures called ribosomes
  5. At the ribosomes the bases on the mRNA are read in threes to code for an amino acid.
  6. The corresponding amino acids are brought to the ribosomes by carrier molecules called tRNA
  7. These amino acids together to form a protein
  8. When the chain is complete the protein folds to form a unique 3d structure.
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14
Q

What are three things that proteins can be?

A

Enzymes-biological catalyst that speed up the rate of reaction
Hormones -chemical messengers that signals around the body
Structural protein -strong proteins in order to form structure such as collagen

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15
Q

What are three ways mutations change the sequence of a base?

A

Insertion
-A base is inserted into the code

Deletion
-A base is deleted from the code

Substitution
-A base is substituted

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16
Q

What is a gamete, chromosome, allele, homozygous, heterozygous, genotype, phenotype

A

Gamete-an organisms reproductive cell which has half the number of chromosomes

Chromosomes -structure found in the nucleus which is made up of long strands of DNA

Allele-different forms of the gene

Homozygous -when both inherited alleles are the same

Heterozygous -when one of the inherited alleles is dominant and the other is recessive

Genotype -the combination of alleles an individual has

Phenotype -the physical characteristics that are observed in the individual

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17
Q

What is polydactyly and what is it caused by?

A

Having extra fingers or toes

Caused by a dominant allele

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18
Q

What is cystic fibrosis and what is it caused by?

A

A disorder of the cell membranes resulting in thick mucus in airways and pancreas

Caused by a recessive allele
-Both parents need to either be carriers or one must have the CF themselves and the other is a carrier

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19
Q

What is embryonic screening?

A

Allows scientist to observe whether a child will have a genetic condition or not

-If the embryo is developed in the lab cells can be taken from it and analysed
-dna from embryos in the womb can also be extracted

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20
Q

What are arguments for embryonic screening?

A

Reduces the number of people suffering-ethical

Treating disorders is very expensive -economic

There are many regulations in place to stop it getting out of hand - social

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21
Q

What are arguments against embryonic screening?

A

Could encourage people to pick characteristics, creating designer babies-ethical

It is expensive to carry out screening -economic

May promote prejudice as it suggests that those with genetic disorders will not live full life or are unwanted-social

Decisions about terminating a pregnancy has to be made -social

The procedure can lead to miscarriage -social

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22
Q

Which pair of chromosomes carries the sex determinating genes?

A

23rd

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23
Q

What is the pair of chromosomes for a female versus a male?

A

XX is female
XY is male

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24
Q

What two things does an organism depend on for the phenotype?

A

Genotype- the genes it inherited

Environment -the place that it lives in

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25
Q

What is evolution?

A

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

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26
Q

What is the theory of evolution?

A

All species have evolved from simple lifeform that first developed more than 3 billion years ago

27
Q

How does evolution by natural selection work?

A

Mutations occur which provide variation between organisms

If a mutation provides a survival advantage , the organism is more likely to survive to breeding age

The mutation will then be passed onto offspring

Over many generations, the frequency of the mutation will increase within the population

28
Q

What is selective breeding?

A

When humans choose which organisms to breed in order to produce offspring with a certain desirable characteristics

29
Q

How does selective breeding work?

A

Parents with desired characteristics are chosen

They are bred together

From the offspring those with desired characteristics are bred together

The process is repeated many times until all the offspring have the desired characteristic

30
Q

What is the issue with selective breeding

A

Inbreeding
- breeding those with similar desirable characteristics means it is likely you are breeding closely related individuals
-this reduces the gene pool

31
Q

What is genetic engineering

A

Modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic

E.g: plant cells have been engineered for disease resistance or to have larger fruits

32
Q

What are the 4 steps of genetic engineering

A
  1. Genes from chromosomes are cut out using restriction enzymes leaving ‘sticky ends’ (short sections of exposed, unpaired bases)
  2. A virus or bacterial plasmid is cut using the same restriction enzyme to also create sticky ends. This also contains an antibiotic marker gene
    3.the loop and gene sticky ends are then joined together by DNA ligand enzymes
  3. The combined loop is placed in a vector such as a bacteria cell and then allowed to multiply as it will now contain the modified gene. As bacteria grows, we can see which ones are resistant to antibiotics. The colonies of bacteria or also producing the modified gene as they were instructed together. Implants the vector is put into meristematic cells which can then produce identical copies of the modified plant
33
Q

Why do we use genetically modified crops?

A

They are engineered to be resistant to insects and to herbicides

This will result in increase yield as less crops will die

34
Q

Why do we use gene modification in medicine?

A

It may be possible to use genetic engineering to cure inherited disorders
It is called gene therapy and it involves transferring normal genes, which are not faulty, into patients so the correct proteins are produced

35
Q

What are the perceived benefits of genetic engineering?

A

-It can be very useful in medicine to mass produce certain hormones in microorganisms
-in agriculture it can be used to improve yields by
Improving growth rates
Introducing modifications that allow the crops to grow in different conditions
Introducing modifications that allow plants to make their own pesticide or herbicide

-With extra vitamin can be produced in areas where they are too difficult to obtain
-Greater yields can help solve world hunger which is becoming an increasing bigger issue due to population growth

36
Q

What are the perceived risks of genetic engineering?

A

-GM crops may have an effect on wildflowers and therefore insects as they are infertile and these jeans could spread into wild plants needing to infertility in other species which would affect the entire environment

-people are worried that we do not completely understand the effects of GM crops on human health

-Genetic engineering in agricultural could lead to genetic engineering and human this may lead to people using technology to have design babies

-They propose a selection which could lead to increase with resistance and other species creating super weeds and pests

37
Q

Describe what happens in tissue culture

A
  1. Plant cells are taken
  2. They are placed in a group medium with nutrients and hormones.
  3. They grow into new plants and our clones as they are genetically identical to the parent.
38
Q

Describe what happens in a cutting

A
  1. Cutting such as a section of the stem are taken from a plant with a desirable feature.
  2. They are planted and produced clones as they are genetically identical to the parent.
39
Q

Describe the purchase of embryo transplant in animals

A
  1. sperm cells and egg cells from parents with desirable features are obtained.
  2. In the lab, they are fertilised to form an embryo.
  3. The embryo divides many times and is then inserted into a host mother
  4. the offspring which is eventually born is genetically identical as they have the same genetic information from the same mother and father
40
Q

Describe the process of adult self cloning in animals

A
  1. The nucleus is removed from unfertilised egg cell
  2. The nucleus is removed from an adult body cell and placed in the denucleated egg cell
  3. Through the stimulation of an electric shock, the egg begins to divide to form an embryo.
  4. The embryo is implanted into the womb of a female.
  5. The offspring born is a clone of the adult body cell.
41
Q

What are the three benefits of cloning?

A

-produces lots of offspring with a specific desirable feature
-The study of clones can help research into embryo development
-Can help extremely endangered species or even bring back species that have become extinct

42
Q

What are the three risks of cloning

A

-the gene pool is reduced through producing clones meaning it is less likely that the population will survive if a disease arises with low diversity in the population
-clones have a low survival rate and tend to have some genetic problems
-It may lead to human cloning

43
Q

Describe the theory of evolution and who it came from

A

Charles Darwin
-Variation exists within species as a result of mutations in DNA
-Organisms with characteristics most suited to the environment are more likely to survive to reproductive age and breed successfully which is called survival of the fittest
-The beneficial characteristics are then passed onto the next generation
-Many generations, the frequency of alleles for this advantageous characteristic increased within the population

44
Q

What were three doubts surrounding Darwins theory

A
  1. Contradicted the idea that God was the creator of all species on earth.
  2. There was not enough evidence at the time as few studies had been done on how organisms change over time.
  3. The mechanism of inheritance variation were not known at the time.
45
Q

What was Lamarck’s theory of evolution?

A
  1. Changes that occurred during the lifetime of an organism were passed onto offspring.
  2. If an individual continually repeated an action characteristic that allowed it to do this would develop further.

For example, if a giraffe stretch to reach leaves on a tree that is high up , its neck would become longer allowing it to do this more easily. This characteristic would then be passed onto its offspring.

46
Q

What proved Lamarck’s theory wrong?

A

When it was understood that changes caused by the environment were not passed on in the sex cells

47
Q

What is speciation

A

Process of a new species developing through the selection of different alleles

48
Q

How did Alfred Russell Wallace develop the theory of evolution

A
  1. On his troubles, he had the idea that individual she did not have characteristics to help them survive a change in the environment would die out
  2. He published joint studies with Darwin.
  3. The publication of the origin of species meant Darwin received credit for the theory.
  4. He continue to work across the world to collect
    evidence.-one of his most important works was on warning coloration in animals
  5. Much more evidence overtime has resulted in our current understanding.
49
Q

Describe the process of speciation

A
  1. Variation exists within a population as a result of genetic mutations.
    2.alleles which provide a survival advantage are selected through natural selection
  2. Population of a species can become isolated for example through physical barriers such as for preventing them from breeding together
  3. Different alleles maybe advantages in the new environment leading them being selected for
  4. Over the time the selection of different alleles will increase the genetic variation between the two populations
  5. When they are no longer able to breed together to produce offspring, a new species transformed.
50
Q

What did Gregor Mendel do to understand genetics?

A

-he carried out breeding experiments on pea plants
-He used smooth peas, wrinkled peas, green peas and yellow peas and observed the offspring to see which characteristics they had inherited

51
Q

What was Gregor Mendel’s conclusion?

A

-offsprings have some characteristics that their parents have because they inherit hereditary units from each
-One unit is received from each parent
-Units can be dominant or recessive and cannot be mixed together

52
Q

Why was Mendel not recognised until after his death?

A

-genes and chromosomes were not yet discovered people could not understand
-in the late 19th century chromosomes as a part of cell division were observed
-In the 20th century it was understood that chromosomes and units had similar behaviours
-Structure of DNA was determined in 1953 which meant we were able to understand how genes worked

53
Q

What are the two evidences for evolution?

A
  1. Fossils.-the remains of organisms from many years ago which are found in rocks.
  2. Antibiotic resistance in bacteria.-the selection pressure of antibiotics lead advantageous mutations being selected for bacteria in populations so they are no longer killed when exposed antibiotics
54
Q

What are the three ways that fossils are formed

A
  1. Parrot shop organisms that have not decayed because oxygen or moisture were not present, meaning that the microbes that caused the decay cannot survive
  2. Parts of the organism such as teeth shells and bones are replaced by minerals as they decay forming a rock structure of the original part
  3. Preserved traces such as footprints, burrows and rootlet traces remain due to the hardening around them and forming a cast
55
Q

What are two reasons why fossils cannot be used to tell us how life on earth started?

A

-most only life forms are soft bodied and therefore decay completely so there are few fossils of them
-Any traces left have been destroyed by geological activity

56
Q

What are the factors which can contribute to extinction?

A
  1. Changes in environment which the species cannot adapt fast enough to.
  2. New predators may have evolved or migrated to the area.
  3. A disease arises and there are no resistant alleles to it
  4. they have to complete with a new species which has advantageous mutations for the same food source
  5. A catastrophic event can wipeout a species.
  6. Destruction of habitat
57
Q

Describe the process of when a bacteria becomes resistant

A

-bacteria reproduce at a fast rate
-Mutations during reproduction can result in new genes such as the gene for antibiotic resistance-this is the creation of a new strain
-exposure to antibiotics creates a selection pressure as those with antibiotic resistant genes survive and those without it die
-Result those with antibiotic resistance can reproduce and pass on the advantageous gene to their offspring
-This population of antibiotic resistant bacteria increases
-Bacterial diseases spread rapidly because people are not immune to these new resistant bacteria and there’s no treatment for it

58
Q

What is an example of resistant bacteria?

A

MRSA
-Called a superbug as it is resistant to many different type of antibiotics
-Hospitals: spread when doctors and nurses moved to different patients

59
Q

How do we slow the development of resistance in bacteria?

A
  1. Antibiotics should not be given for viral or non-serious infections.
  2. Specific antibiotic should be given for specific bacterial.
  3. Patient should complete their course of antibiotics.-if they do not run bacteria may survive and mutate to become antibiotic resistant
  4. Antibiotics should be used less in agriculture-farmers use them to prevent their livestock dying from disease but this overuse leads to antibiotic resistant bacteria which are then transferred to humans when they consumed the meat
60
Q

How do we slow down the transmission of bacteria?

A
  1. Maintain high standards of hygiene in hospitals.
  2. Medical staff and visitors should wash hands regularly.
  3. Medical staff should wear disposable clothing or clothing that is regularly sterilised.
61
Q

What was the Linnaean system?

A

Living things were divided into kingdom phylum class order family genus species

62
Q

What is the binomial system?

A

The first part is their genus - second is their species

-for instance, humans are referred to as Homo sapiens

63
Q

What is the three domain system?

A

-Above kingdom, carl woese I did three large groups called domains

Archaea- primitive bacteria which live in extreme environment such as hot springs
Bacteria -true bacteria
Eukaryota- organisms who have a nucleus enclosed in membranes

64
Q

What are evolutionary trees?

A

Used to show how closely related organisms are

BIOLOGY PAPER 2 (3 decks)

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