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Biology > Topic 6 (P2) > Flashcards

Topic 6 (P2) Flashcards

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1
Q

Describe the structure of DNA

A

A polymer made up of two strands coiled together in a double helix.

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2
Q

What is a genome?

A

Entire set of genetic material of an organism.

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3
Q

What is the monomer for DNA?

A

Nucleotides

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4
Q

What are the parts of a nucleotide?

A

.Phosphate
.Sugar
.Base

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5
Q

What is the code for an amino acid?

A

A sequence of 3 bases.

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6
Q

What do the order of bases control?

A

The order in which amino acids are assembled which produce a particular protein.

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7
Q

Explain the process of protein synthesis

A

Transcription
.A small copy of a gene is made= mRNA
.mRNA is only a single strand so can pass out of nucleus into cytoplasm

Translation
.mRNA attaches to a ribosome
.tRNA carries amino acids to the ribosome
.ribosome reads the mRNA and joins together correct amino acid in correct place
.this chain of amino acids is a poly-peptide which folds to form a protein

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8
Q

What differences are there in structure between DNA and mRNA?

A

1) mRNA is shorter
2)mRNA is a single strand
3)Contains U base instead of T

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9
Q

What are the 3 uses of proteins and what are their functions?

A

1) Enzymes- biological catalysts that speed up reactions in the body
2) Hormones- carry messages around the body
3) Structural proteins which are physically strong (e.g. collagen to strengthen ligaments)

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10
Q

What’s a mutation?

A

A change to a base.

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11
Q

True or false: Most mutations have an effect on a protein
Explain.

A

False because sometime a base might have changed but doesn’t change the amino acid sequence because different bases can sometimes code for the same amino acid

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12
Q

What does changing the shape of a protein do?

A

Changes it’s function

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13
Q

Give an example of when a mutation that changes the shape of a protein can have a dramatic effect?

A

Active site of an enzymes might change so can’t attach to substrate.

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14
Q

What do non-coding chromosomes do?

A

Control if a gene is expressed or not (turn it on or off)

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15
Q

What might a mutation to a non-coding chromosome do? Use an example.

A

Might switch on a gene that should be turned off e.g. uncontrolled mitosis leading to cancer.

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16
Q

Explain the two types of mutations that can change more than one amino acid because it has a knock-on effect

A

Insertion- a new base is inserted into DNA base sequence
Deletion- a random base in the DNA sequence is changed to a different base

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17
Q

Explain the type of mutation that only changes one amino acid because it doesn’t have a knock on effect

A

Substitution- a random base is changed to a different base

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18
Q

What are gametes?

A

The reproductive cells

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19
Q

How many chromosomes are in each gamete and why?

A

23 so that when the egg and sperm cell fuse it makes the whole amount (46)

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20
Q

What are the gametes in plant reproduction?

A

Egg cell
Pollen

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21
Q

Who reproduces asexually?

A

Bacteria, some plants, some animals

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22
Q

Does ASEXUAL reproduction happen my mitosis or meiosis?

A

MITOSIS

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23
Q

Does SEXUAL reproduction happen by mitosis or meiosis?

A

MEISOSIS

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24
Q

Where does meiosis occur in the human body?

A

Males- testes
Females- ovaries

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25
Explain the process of meiosis
1)The chromosomes are copied 2)The cells divides into two daughter cells 3)These two cells divide again to produce in total 4 genetically different cells 5)Each cell has half the number of chromosomes as original cell
26
What are the advantages of SEXUAL reproduction?
1) Variation in offspring 2) If environment changes, variation in offspring gives survival advantage by natural selection
27
What are the ASEXUAL reproduction?
1)Less time 2)Less energy 3)Only one parent needed
28
Give some examples of organisms that reproduce both sexually and asexually
Malarial protists reproduce asexually in the human host but sexually in the mosquito. Strawberry plants
29
Explain 2 inherited disorders and the type of allele they are caused by.
Cystic Fibrosis (caused by recessive allele) =disorder of the cell membrane causing a lot of thick mucus being produces in the air passages and the pancreas. Polydactyl (caused by a dominant allele) =having extra fingers or toes
30
What are the pros of embryo screening?
1)help stop people suffering 2)treating disorders costs the government and taxpayers a lot of money
31
What are the cons of embryo screening?
1) expensive to carry out 2)risk of damaging the embryo 3)may be seen as unethical as embryos cannot consent
32
Explain the theory of evolution by natural selection (Charles Darwin)
.Organisms with suitable characteristics for the environment are more likely to survive and reproduce -passing on gene that made them successful to the offspring .Organisms that are less well adapted are less likely to survive and reproduce so less likely to pass down genes to next generation .Over multiple generations, beneficial characteristics become more common and species evolves
33
How does a new species occur?
.Organisms with suitable characteristics for the environment are more likely to survive and reproduce -passing on gene that made them successful to the offspring .Organisms that are less well adapted are less likely to survive and reproduce so less likely to pass down genes to next generation .Over multiple generations, the phenotype of an organism an change so much that it becomes a new species and cant breed with other species
34
Give an example of a phenotype.
.eye colour, blood type
35
Give one reason it took a while for Mendel's work to be accepted. Give one reason why it might have been accepted.
When he published his findings, scientists didn't know about genes and DNA. In the late 1800s scientists became familiar with chromosomes and how they acted during cell division. And in the 20th century, the structure was DNA was determined.
36
What are the three ways for variation to occur?
.Genetic variation .Environment (e.g language) .A combination of both (e.g height)
37
What did scientists believe about inherited characteristics before Mendel? Give one way Mendel's experiment proved this wrong.
Many scientists believed that characteristics were blended when they were inherited. One example to disprove is Mendel saw that the shape of the pea pod had no effect on the colour of the flower.
38
What were Mendel's 3 conclusions?
1) Characteristics in plants are determined by 'hereditary units' 2) Hereditary units are passed on to offspring unchanged from both parents 3) Hereditary units can be dominant or recessive
39
Describe the process of natural selection using the example of rabbits getting thicker fur. The, explain how this might lead to speciation.
.The environment gets colder .Rabbits that inherited alleles for thicker fur will be more likely to survive the cold conditions .So, more likely to reproduce and some of it's offspring could inherit the thicker fur allele .That offspring is more likely to survive and pass down it's thicker fur allele .Over many generations, alleles for thicker fur become more common and overall more rabbits have thicker fur Sometimes 2 populations of one species become so different in phenotypes that they cannot produce fertile offspring. So there are now 2 different species.
40
State 3 findings found in Charles Darwin's On the Origin of Species
.Individual organisms within a species show a wide range of variation .Individuals with characteristics most suited to the environment are more likely to survive and breed successfully .The characteristics that have enabled these individuals to survive are then passed on to the next generation
41
Why was there opposition to Darwin's theory?
.During this very religious time, the theory challenged that God made all the plants and the animals .There was insufficient evidence- understanding of inheritance and variation came around 50 years after
42
What was Lamarck's theory?
If a characteristic is regularly used, it becomes strengthened. This strengthened characteristic gets passed on to offspring.
43
Why is Lamarck's theory incorrect?
In the majority of cases, changes that occur during an organisms lifetime cannot be passed on to offspring
44
State the 4 reasons for selective breeding.
.Animals that produce more meat or milk .Dogs to be docile and good-tempered .Crops with a disease resistance .Plants with large or unusual flowers
45
Explain the process of selective breeding.
.From existing stock, select the ones with desired characteristics .Breed them together .Select the best offspring and breed them together .Continue this process over multiple generations and the desirable traits should get stronger .Eventually all the offspring will have the characteristics
46
What is the main drawback of selective breeding?
It can lead to inbreeding where some breeds are particularly prone to disease or inherited defects.
47
Explain the process of genetic engineering.
1) Identify the gene you want to transfer 2) Use enzymes to isolate it 3) Insert gene into a bacterial plasmid or a virus 4) These act as vectors to transfer desired gene to organism
48
At what stage of the organism's development do you transfer the gene?
Early stages
49
Give 2 examples of the uses of genetic engineering. And, give one potential use for the future
.Bacteria have been genetically modified to produce human insulin to treat diabetes .Plant crops have been genetically modified to produce bigger fruit and to be resistant to certain diseases. Overall, this increases yield. In the future, it's a possibility GM can be used for gene therapy- to treat inherited diseases
50
What are 2 cons of GM crops?
.Some are concerned that GM crops will reduce biodiversity .Some are concerned that we might not fully understand the effects of eating them on human health
51
What is extinction? Why might it happen?
= species no longer exists anywhere on earth .New disease kills them all .Environment change stop quickly (e.g destruction of habitat)
52
What is tissue culture? Who uses it and for what?
=where you take a few plant cells and put in a growth medium with hormones to produce identical clones .Scientists to preserve rare plant species .Plant nurseries to produce lots of stock quickly
53
What is cuttings? Who uses it and why?
=where you take a cutting from a good parent plant to produce identical clones .Gardeners because it is quick and cheap. It is more simple than tissue culture
54
What are embryo transplants?
=splitting apart cells from an animal embryo before they become specialised, then transplanting the identical embryos into host mothers
55
Explain the method of adult cell cloning
* The nucleus is removed from an unfertilised egg cell * The nucleus from an adult body cell, such as a skin cell, is inserted into the egg cell. * An electric shock stimulates the egg cell to divide to form an embryo. * When the embryo has developed into a ball of cells, it is inserted into the womb of an adult * Grows into an identical clone of adult body cell with the same genetic information
56
Give a pro and 2 cons of cloning (1 reason, 1 ethical reason).
Pro: .Preserve endangered species Con: .Reduce gene pool- if population closely related, if there's a new disease introduced, all could be wiped out as there might not be a allele for resistance to it.
57
What are fossils and what do they show?
Fossils= remains of organism many thousands of years ago that are found in rocks. They show how little or how much organisms have evolved.
58
Explain the 3 ways that fossils might have been formed.
1) .Things like teeth, shells and bones can last a long time when buried .They are eventually replaced by minerals as they decay forming a rock-like substance shaped like the original hard part 2) .Some organism are buried in soft material .The material eventually hardens leaving a cast of itself. Also works for footsteps 3) .In amber and tar pits, there is no oxygen so decay microbes can't survive .In glaciers it is too cold for the decay microbes to work .Sometimes it's to acidic for decay microbes
59
Why don't fossils explain how life began?
.Early life forms were soft bodied so tended to decay completely so the fossils were incomplete .Fossils that did form millions of years ago may have been destroyed by geological activity
60
Who worked on the idea of speciation?
Wallace
61
Explain the process of speciation.
.A population of organisms become geographically separated .The environment is slightly different on each side of the barrier so natural selection causes different characteristics so develop in each population .Isolation prevents the 2 populations from interbreeding and sharing alleles .Over time, the two population's genes will become so different that they can't reproduce to make fertile offspring .2 species have formed
62
Why can bacteria evolve so rapidly?
They reproduce every 20 minutes
62
Name one superbug.
MRSA
63
How can we reduce the rate of antibiotic resistant strains?
1. Agricultural use of antibiotic's should be restricted 2.Not use it for viral infections 3. Complete course of antibiotics so all bacteria are killed and none can survive to mutate and form resistant strains
64
Explain the process of how superbugs occur.
.In an ordinary population of bacteria, some bacteria, some bacteria may have antibiotic resistant strains .Those that have the strains are not killed by the antibiotic (and thrive because little competition) and reproduce .They might pass on the resistant strain to offspring so population of resistant strain increases .Will spread because people are not immune and there's no effective treatment
65
Why can't doctors just create new antibiotics against the superbugs.
The development of new antibiotics is costly and slow. It won't be able to keep up with the emergence of new resistant strains.
66
Who first developed a system for classifying living things?
Linnaeus
67
List the Linnaeus system and the mnemonic.
Kingdom Phylum Class Order Family Genus Species King Philip Craves Our Fat Git Soup
68
How are living things now classed?
Three domain system: Archaea- primitive bacteria Bacteria- true bacteria such as the ones in the human digestive system Eukaryota- includes animals, plants, fungi, protists
69
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