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CCEA GCSE Biology > Genetic Diagrams & Terminology > Flashcards

Genetic Diagrams & Terminology Flashcards

1
Q

Pedigree chart

(3 marks)


A

A family tree diagram which show the inheritance of a genetic condition in a family, eg cystic fibrosis.

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2
Q

Phenotype

2 marks

A

The visible characteristics of an organism which occur as a result of its genes.

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3
Q

Characteristics are passed from

1 mark

A

Parents to offspring.

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4
Q

Humans have 1.__ chromosomes arranged into 2.__ pairs.

2 marks

A
  1. 46

2. 23

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5
Q

Small section of DNA that codes for a characteristic (e.g. eye colour)

(1 mark)

A

Gene

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6
Q

Different forms of the same gene - eg blue + brown are both _______ of the eye colour gene.

(1 mark)

A

Alleles

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7
Q

Similar genes occupy the same position on both chromosomes in the pair of

(1 mark)

A

Alleles

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8
Q

Monohybrid genetic crosses

4 marks

A

Genetic diagrams consisting of a single characteristic controlled by a single gene with 2 alleles.

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9
Q

Alleles can be

2 marks

A

Dominant or recessive.

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10
Q

Dominant alleles

1 mark

A

Will be expressed even if a recessive allele is present.

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11
Q

Recessive alleles

1 mark

A

Will be overridden by the presence of a dominant allele.

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12
Q

2 recessive alleles (no dominant) need to be present for

2 marks

A

The recessive characteristic to be expressed in the phenotype.

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13
Q

The phenotype is the outward expression of a

1 mark

A

Gene (i.e. the physical appearance).

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14
Q

The Genotype

4 marks

A
  • Set of paired symbols used to represent the alleles present.
  • Can be homozygous (the same, BB or bb) or heterozygous (different, Bb).
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15
Q

Homozygous

3 marks

A

The same

  • a genotype can be Homozygous (BB/bb) or Heterozygous (Bb).
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16
Q

Heterozygous

3 marks

A

Different

  • a genotype can be Heterozygous (Bb) or Homozygous (BB/bb)
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17
Q

During 1._______, gametes with 2.____ ___ gene for each characteristic are produced,
- meaning parents can only pass on 3.___ allele for each characteristic to their offspring.

(2 marks)

A
  1. Meiosis
  2. Only one
  3. One
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18
Q

Made the observation that pea plants had characteristics that varied from plant to plant.

(1 mark)

A

Gregor Mendel

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19
Q

Gregor Mendel birth - death years

2 marks

A

1822 - 1884

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20
Q

Carried out experiments crossing (mating) plants with different characteristics.

(2 marks)

A

Gregor Mendel

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21
Q

How was Gregor Mendel able to draw conclusions about the inheritance of characteristics?

(1 mark)

A

By observing the characteristics of the offspring produced.

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22
Q

Conclusion of Gregor Mendel findings

8 marks

A
  • Characteristics are determined by factors within the organism (now known as genes)
  • Genes can be present in 2 different forms (now known as alleles)
  • 2 alleles in an individual separate during gamete formation (now known as meiosis)
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23
Q

What did Gregor Mendel not know of, other than their basic functions?

(3 marks)

A

Chromosomes, Genes or Meiosis.

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24
Q

Characteristics are determined by

2 marks

A

Factors within the organism - now known to be genes.

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25
Q

Factors (genes) can be present in

2 marks

A

2 different forms - now known as alleles.

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26
Q

2 factors (alleles) in an individual separate during

2 marks

A

Gamete formation - now known as meiosis.

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27
Q

Gamete formation

1 mark

28
Q

Punnett squares

2 marks

A

A grid used to determine genotype frequencies.

29
Q

Example of genotype frequencies determined by Punnett Squares

(1 mark)

A

Plant height

30
Q

T = ____ allele

1 mark

31
Q

t = _____ allele

1 mark

32
Q

Tall Allele symbol

1 mark

33
Q

Small allele symbol

1 mark

34
Q

Purebred tall plants can be obtained by

1 mark

A

Only allowing tall plants to breed with other tall plants for a period of time.

35
Q

Purebred short plants can be obtained by

1 mark

A

Only allowing short plants to breed with other short plants over a period of time.

36
Q

Crossing purebred tall (homozygous dominant – TT) + short parent plants (homozygous recessive – tt) results in

(4 marks)

A

First generation (F1) offspring all being tall (heterozygous – Tt).

37
Q

Purebred Tall Parent Plants

3 marks

A

Homozygous dominant – TT

38
Q

Purebred Short Parent Plants

3 marks

A

Homozygous recessive – tt

39
Q

First generation offspring

1 mark

40
Q

Purebred Tall Parent Plant x Purebred Small Parent Plant = Tall ___________ - ____

(2 marks)

A

Heterozygous – Tt

41
Q

Alleles - 1:0 ratio

Homozygous Parents:

Mothers gametes - BB
Fathers gametes - bb

(5 mark)

A

In these offspring, dominant allele (B) overrides the recessive allele (b)

= offspring phenotype having brown eyes.

42
Q

Alleles - 3:1 ratio

2 Heterozygous Parents:

Mothers gametes - Bb
Fathers gametes - Bb

(2 marks)

A

Offspring has 75% chance of having brown eyes + 25% chance of having blue eyes.

43
Q

Alleles - 1:1 ratio

1 Heterozygous Parent + 1 Homozygous Parent:

Mothers gametes - Bb
Fathers gametes - BB

(2 marks)

A

Offspring has 50% chance of having blue eyes + 50% chance of having brown eyes.

44
Q

Dominant alleles in eye colour

2 marks

A

Brown eyes are Dominant - B

45
Q

Recessive alleles in eye colour

2 marks

A

All eye colours except Brown eyes are recessive + especially Blue eyes - b

46
Q

Needs to be produced to provide an accurate ratio

1 mark

A

Large numbers of offspring.

47
Q

Why do large numbers of offspring need to be produced to provide an accurate ratio? (In Punnett squares)

(1 mark)

A

Because fertilisation is random.

48
Q

Test (back) cross

5 marks

A

Genotypes TT + Tt both produce a tall phenotype

  • In order to establish the genotype, a test cross is used.
49
Q

How is a Test Cross used

8 marks

A

Organism is crossed with a homozygous recessive individual (tt).

  • no short plants (tt) present in the offspring = unknown parent was homozygous (TT).
  • short plants (tt) are present in the offspring = unknown parent was heterozygous (Tt).
50
Q

Pedigree diagrams

1 mark

A

Used to show how a genetic condition is inherited in a family.

51
Q

Reason pedigree diagrams are often used

2 marks

A

To advise individuals within a particular family if they are carriers of a condition.

52
Q

Phenotype: Tall - with Heterozygous parents

Genotype:

(1 mark)

53
Q

Phenotype: Tall - with Homozygous parents

Genotype:

(1 mark)

54
Q

Phenotype: Small - with Homozygous parents

Genotype:

(1 mark)

55
Q

Meiosis

2 marks

A

Reduction division in a cell in which the chromosome number is halved from diploid to haploid.

56
Q

Mucus

2 marks

A

Slimy white protein, which lines the respiratory tract + alimentary canal.

57
Q

Recessive

2 marks

A

An allele that will only show in the phenotype if there is no dominant allele present

(i.e. when 2 recessive alleles are present).

58
Q

In males the sex chromosomes are __________.

3 marks

A

Heterozygous – 1 X + 1 Y chromosome.

59
Q

In females the sex chromosomes are ____________.

3 marks

A

Homozygous – 2 X chromosomes.

60
Q

Karyotype

1 mark

A

An image of a complete set of chromosomes.

61
Q

Meiosis forms

2 marks

A

Haploid gametes (sperm + egg cells).

62
Q

All eggs contain

1 mark

A

1 X chromosome.

63
Q

50% of sperm contain 1 __ __________ + 50% contain 1 __ __________

(2 marks)

A
  • X Chromosome

- Y Chromosome

64
Q

During fertilisation, there is a 50% chance that

8 marks

A
  • A sperm containing an X chromosome will fuse with the egg; this would result in a baby girl – XX.

OR

  • A sperm containing a Y chromosome will fuse with the egg; this would result in a baby boy – XY.
65
Q

Within a population there will be equal numbers of

1 mark

A

Females + males.

CCEA GCSE Biology (33 decks)

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