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GCSE Biology > B5 Genes, inheritance, and selection > Flashcards

B5 Genes, inheritance, and selection Flashcards

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1
Q

Definition of phenotype

A
  • The physical expression of the genes

- The appearance of an organism

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2
Q

Give examples of genetic variation

A

Eye colour
Ear lobe
Ability to roll your tongue
Blood group

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3
Q

What are the two causes of variation?

A
  • Genetic variation

- Environmental variation

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4
Q

What is genetic variation?

A

Variation caused by the genetic material you inherit from your parents

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5
Q

What is environmental variation?

A

Variation caused by the environment in you you live

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6
Q

What are the two types of variation?

A

Continuous variation

Discontinuous variation

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7
Q

Give examples of environmental variation

A

Accent
Dialect
Taste
Skills

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8
Q

Give an example of a characteristic that is affected by both environmental and genetic variation.

A

Height- it is mostly determined by your genes so if your parents are tall, you are also likely to be tall. However, if your diet is very poor you may not grow to your full potential height.

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9
Q

What causes continuous variation?

A

Genetic and environmental

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10
Q

Definition of continuous variation

A

continuous variation can take a value within a range

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11
Q

Genetic control in discontinuous variation

A

Genetic

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12
Q

Definition of variation

A

Difference within a species

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12
Q

What causes discontinuous variation?

A

Genetic

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14
Q

Definition of discontinuous variation

A

Discontinuous variation…
…can only result in specific (discrete) values
…characteristic that falls into distinct groups

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15
Q

What type of graph is used to display data for discontinuous data?

A

Bar chart

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16
Q

Examples of discontinuous variation

A

Gender
Eye colour
Wrinkled or non- wrinkled seeds
Blood group

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17
Q

Examples of continuous variation

A

Leaf surface area
Length of fur
Skin colour
Height

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18
Q

Definition of a clone

A

A clone is an organism that is genetically identical to its parent.

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19
Q

Genetic control in continuous variation

A

Multiple genes

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21
Q

What is asexual reproduction?

A

It involves one parent which means there is no mixing of genetic material so each new organism contains identical genes, which are genetically identical to the parent. This occurs by the process of mitosis.

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22
Q

Give examples of organisms that can reproduce asexually.

A

Bacteria
Potato plants- produce many tubers, each of which can grow into a new plant
Spider plants- produce long stems, known as runners, with tiny plants (plantlets) on the end.
Daffodils- produce an underground food storage organ (a bulb) at the end of each growing season. The following year a new flower will grow from a bud on this bulb.
Sea anemones
Star fish

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23
Q

What type of graph is used to display data for continuous variation?

A

Line graph

Histogram (often the bars are removed and just the line showing the trend shown)

23
Q

What are somatic cells?

A

Cells that aren’t sex cells

24
Q

Name an organism that can reproduce both sexually and asexually.

A

Sea anemones

25
Q

Disadvantages of asexual reproduction

A

There is no genetic variation between offsprings so if the environment changes and the conditions become unfavourable, the whole population can be affected.

26
Q

What are diploid cells?

A

Normal body cells (somatic cells)

They contain 46 chromosomes

28
Q

Advantages of sexual reproduction

A

Creates genetic variation within the population which leads to adaptations. This means that if the environmental conditions change, it’s more likely that some individuals will have characteristics that enable them to survive. This leads to evolution as species become better adapted to their environment.

28
Q

Disadvantages of sexual reproduction

A
  • it take more time and energy than asexual reproduction as they need to find a mate so organism produce fewer organisms in a lifetime.
  • Two parents are needed for sexual reproduction which can be a problem if the individual are isolated. Eg. Polar bears often live alone, so male polar bears may have to walk up to 100 miles to find a mate.
29
Q

What is binary fission?

A

How bacteria reproduce.

30
Q

What are haploid cells?

A 
Gamete cells (ova and sperm cells) are haploid cells.
They contain half the number of chromosomes of normal cells so 23 chromosomes.
31
Q

Definition of genome

A

The entire genetic material of an organism

32
Q

Where does meiosis occur in humans?

A

Ovaries and testes

33
Q

Advantages of asexual reproduction

A
  • Asexual reproduction can produce lots of offsprings very quickly as only one parent is involved so the organism does need to find a mate/partner.
  • if the parent is well adapted to an rea, the offspring will share an identical set of characteristics.
35
Q

What is a dominant allele?

A

It will always be expressed if they are present in its genetic material.
It is shown by a capital letter

36
Q

Thought what process do zygote cells go through to produce new organisms?

A

Mitosis

37
Q

How are gametes produced?

A

They are produced through a type of cell division called meiosis.

38
Q

Definition of genotype

A

The combination of alleles present in an organism

39
Q

What is a zygote?

A

It is diploid cells that is formed when during fertilisation two haploid gamete cells join together.

40
Q

Definition of homozygous recessive

A

If you have two copies of the recessive allele. Eg. bb

41
Q

Explain the first stage of meiosis.

A

1) Before the cell starts to divide the chromosomes are copied.
2) The chromosomes then line up in pairs in the centre of the cell. (One from the mother, one from the father)
3) The pairs are them pulled apart to opposite ends of the cell ( when they are pulled apart, often sections of DNA are swapped)
4) the cell than divides in two
5) Two separate cells are formed

42
Q

Definition of alleles

A

Alternate forms of a gene

42
Q

What is a recessive allele?

A

This characteristic is only expressed if you have two copies of the allele.
It is shown by a lower case letter.

44
Q

Definition of homozygous dominant

A

If you have two copies of the dominant allele. Eg. BB

45
Q

Explain the second stage of meiosis

A

6) In the second stage the chromosomes line up along the middle of each of the two new cells.
7) This time each chromosome is pulled in half. A single copy of each chromosome goes to opposite ends of the cell.
8) Each cell then divide into two. This results in four haploid cells.

45
Q

Definition of heterozygous

A

If you have two different alleles for that articulate gene. Eg. Bb

46
Q

What sex chromosomes so males have?

A

XY

So the father determines the sex of its offspring.

47
Q

What affect do mutations have in coding DNA?

A

Mutations in coding DNA affect the proteins coded for by the gene. This can affect the protein’s structure and the way that is functions. Eg. The active site of an enzyme may be altered so that it can no longer bind with its substrate meaning it can no longer function.

48
Q

What is a genetic variant?

A

It is a different version of an allele, which is caused by a change in the DNA. All variant arise from mutations.

49
Q

What sex chromosomes do females have?

A

XX

49
Q

What are sex chromosomes?

A

They are the 23rd pair of chromosomes in a human body cell.

50
Q

Explain Gregor Mendel’s experiment on tall and dwarf pea plants.

A

1) Mendel crossed a tall pea plant with a dwarf pea plant. All the offspring were tall.
2) So, Mendel took two of the tall plants from the first set of offspring and crossed them. This time 75% off the offspring were tall but 25% were dwarf plants.
3) Mendel has shown that the height characteristic in pea plants was determined by separate inherited factors passed on from each parent. The ratios of tall and dwarf plants in the offspring showed that the factor for tall plants was dominant over the factor for dwarf plants.

52
Q

Definition of mutation

A

A random inheritance to sequence of bases on DNA
It occurs when the sequence of DNA bases is altered.
Mutations can occur spontaneously

53
Q

What affect do mutations have on non-coding DNA?

A

Mutations in non-coding DNA can affect how genes are expressed i.e whether or not genes are switched on. They can stop the transcription of mRNA so the protein coded for by that gene is not produced at all.

GCSE Biology (4 decks)

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