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b6 Flashcards

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1
Q

Which type of cell division leads to identical cells being formed?

A

Mitosis

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2
Q

Name the gametes (sex cells) in animal reproduction.

A

Sperm (male) and egg (female)

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3
Q

Which type of reproduction leads to a variety in the offspring as there is mixing of genetic information?

A

Sexual reproduction

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4
Q

What is a clone?

A

Genetically identical offspring (a result of asexual reproduction)

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5
Q

Which type of cell division leads to non-identical cells being formed?

A

Meiosis

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6
Q

Name the gametes (sex cells) in plant reproduction.

A

Pollen (Male) and egg cells (female)

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7
Q

Which type of reproduction leads to genetically identical offspring?

A

Asexual reproduction

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8
Q

Before meiosis, there are 46 chromosomes in a human body cell. How many are there in each gamete after meiosis?

A

23

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9
Q

Describe the structure of DNA

A

A polymer made up of two strands forming a double helix.

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10
Q

What is the name for a specific section of DNA that codes for a particular protein?

A

A gene

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11
Q

What is the genome of an organism?

A

The entire genetic material of that organism

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12
Q

Give three reasons why understanding the human genome is important.

A

Genes linked to different types of disease can be searched for
Inherited disorders can be understood / treated
Migration patterns of the past can be traced

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13
Q

Before cell division, what does the DNA in the cell get stored in?

A

Chromosomes

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14
Q

What does a gene code for?

A

A particular sequence of amino acids, which make specific proteins

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15
Q

Complete the Punnett square for the % chance of having a mouse with black fur.

F = brown fur, f = black fur

A

0% chance of having a mouse with black fur

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16
Q

What is embryo screening?

A

Removing a cell from an embryo and analysing its DNA to look for genetic disorders

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17
Q

Explain what is meant by a ‘dominant allele’

A

The characteristic is expressed if one or two copies of the allele is present

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18
Q

What name is given to two of the same alleles (e.g TT or tt)?

A

homozygous

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19
Q

What does ‘genotype’ mean?

A

What alleles an organism has, e.g. Tt, TT or tt

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20
Q

Give an example of characteristics controlled by a single gene

A

Fur colour in mice / red-green colour blindness in humans

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21
Q

Is polydactyly caused by a dominant or recessive allele?

A

Dominant

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22
Q

Complete the Punnett square for the % chance of having a boy or girl

A

50% male, 50% female

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23
Q

What is cystic fibrosis?

A

A genetic disorder that affects cell membranes and causes mucus build up in the air passages and pancreas.

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24
Q

Is cystic fibrosis caused by a dominant or recessive allele?

A

Recessive

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25
Are most characteristics determined by a single gene, or by multiple genes interacting?
Multiple genes interacting
26
What is polydactyl
An inherited disorder that causes a person to have extra fingers or toes.
27
How many pairs of chromosomes are found in ordinary human body cells?
23
28
22 pairs of chromosomes determine an organism’s characteristics, but what does the 23rd pair determine?
The 23rd chromosome determines sex (XX in female and XY in male)
29
What is variation?
Differences in the characteristics of individuals in a population
30
Which of the following is true? a) Most mutations of DNA cause a change in phenotype b) Most mutations of DNA do not cause a change in phenotype
b) Most mutations of DNA do not cause a change in phenotype
31
As well as genotype, what else affects the phenotype of an organism?
The environment
32
What causes genetic variation?
Mutations
33
What is evolution?
A change in the inherited characteristics of a population over time which may result in the formation of a new species
34
When are two organisms with a common ancestor considered to be two different species?
When they cannot interbreed and produce fertile offspring.
35
Describe how selective breeding works
Choosing parents with a desired characteristic Breed them Select offspring with the desired characterstic Breed them Continue over many generations until you have a population with the desired characteristic
36
Give two examples of “desired characteristics” in the selective breeding of animals
Animals which produce more milk / meat Domestic dogs of a gentle nature
37
According to the theory of evolution by natural selection, what have all species of living things evolved from?
Simple life forms that first developed more than three billions years ago
38
Describe how speciation occurs
Isolation of two populations. Differences in environmental conditions or food availability in the two areas. Natural variation in populations. Mutations occur. Individuals that are better adapted to their environment survive, reproduce and produce offspring. Populations become so genetically different that they can’t interbreed and produce fertile offspring
39
Give two examples of “desired characteristics” in the selective breeding of plants
Disease resistance in food crops Large / unusual flowers
40
What are the negative consequences of selective breeding?
Inbreeding causes a reduction in gene pool. Reduced variation in genes means the population is less resistant to disease Inbreeding can cause populations to have genetic defects.
41
Explain what is meant by a ‘recessive allele’
The characteristic is only expressed if two copies of the allele are present.
42
What name is given to two different alleles (e.g Tt)?
heterozygous
43
What is an allele?
A version of a gene
44
Give an example of characteristics controlled by a single gene
Fur colour in mice / red-green colour blindness in humans
45
What is genetic engineering?
Taking a gene from one organism and inserting it into the genome of another.
46
Which organisms have been genetically engineered to produce insulin?
Bacteria
47
What are genetically modified (GM) crops?
Crops that have been genetically engineered (had genes from other organisms inserted into them)
48
What is gene therapy?
The use of genetic engineering to treat inherited diseases caused by faulty genes
49
Give two reasons for genetic engineering plants
Examples include: Disease resistance Pest resistance Drought resistance Produce bigger fruits
50
What are the two main concerns about GM crops?
The effect on populations of wild flowers and insects Human health (not being fully explored)
51
What happens during fertilisation?
The nuclei of the gametes fuse togethe
52
How many cells are produced in meiosis?
4 cells (all genetically different)
53
What is a gamete?
A sex cell (e.g. sperm or egg)
54
Describe the process of meiosis
1) Copies of the genetic information are made (to make chromosomes with two identical arms) Chromosomes line up as pairs and mixing of genetic information occurs. 2) The first cell division takes place and the chromosome pairs are pulled apart. This results in two cells. 3) The chromosomes line up again. 4) A second cell division pulls the arms of the chromosomes apart. This results in four genetically different cells.
55
What are the three main types of fossils?
Parts of organisms that have not decayed because one or more the conditions for decay was absent. Parts of the organism are replaced by minerals as they decay. Preserved traces (footprints / burrows etc…)
56
Why are there very few traces of early life forms?
They were soft-bodied (fossil record incomplete)
57
What is extinction?
When there are no remaining individuals of a species still alive
58
Why can bacteria evolve rapidly?
They reproduce at a fast rate
59
What is MRSA resistant to?
Antibiotics
60
What do fossils show?
How organisms evolved as life developed on Earth
61
Give three causes of the extinction of a species
Any three from: Environmental changes New predators New diseases Catastrophic events Can’t compete for food
62
How do new strains of bacteria occur that are resistance to antibiotics?
Random mutations that cause antibiotic resistance
63
Give three ways antibiotic resistance can be reduced?
Reduce prescription of antibiotics, especially when inappropriate (e.g. for a viral infection) Patients should complete course of antibiotics so all bacteria are killed Restriction of agricultural antibiotic use
64
Who developed the three-domain system of classification?
Carl Woese
65
What are the categories for the Linnaean system of Classification?
Kingdom Phylum Class Order Family Genus Species
66
What caused new models of classification to be proposed?
Evidence of internal structures (using microscopes) and biochemical processes were better
67
In an evolutionary tree, which organisms are most closely related?
The species that are connected by the shorted paths on the evolutionary tree.
68
Who developed the Linnaean system of classification?
Carl Linnaeus
69
What two categories of the Linnaean system make up the binomial system for naming organisms?
Genus and species
70
What are the three-domains in the ‘three-domain’ system?
Archaea (primitive bacteria) Bacteria (true bacteria) Eukaryota (protists, fungi, plants and animals)

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