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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
Factors (genes) can be present in | 2 marks
2 different forms - now known as alleles.
26
2 factors (alleles) in an individual separate during | 2 marks
Gamete formation - now known as meiosis.
27
Gamete formation | 1 mark
Meiosis
28
Punnett squares | 2 marks
A grid used to determine genotype frequencies.
29
Example of genotype frequencies determined by Punnett Squares (1 mark)
Plant height
30
T = ____ allele | 1 mark
Tall
31
t = _____ allele | 1 mark
Short
32
Tall Allele symbol | 1 mark
T
33
Small allele symbol | 1 mark
t
34
Purebred tall plants can be obtained by | 1 mark
Only allowing tall plants to breed with other tall plants for a period of time.
35
Purebred short plants can be obtained by | 1 mark
Only allowing short plants to breed with other short plants over a period of time.
36
Crossing purebred tall (homozygous dominant – TT) + short parent plants (homozygous recessive – tt) results in (4 marks)
First generation (F1) offspring all being tall (heterozygous – Tt).
37
Purebred Tall Parent Plants | 3 marks
Homozygous dominant – TT
38
Purebred Short Parent Plants | 3 marks
Homozygous recessive – tt
39
First generation offspring | 1 mark
F1
40
Purebred Tall Parent Plant x Purebred Small Parent Plant = Tall ___________ - ____ (2 marks)
Heterozygous – Tt
41
Alleles - 1:0 ratio Homozygous Parents: Mothers gametes - BB Fathers gametes - bb (5 mark)
In these offspring, dominant allele (B) overrides the recessive allele (b) = offspring phenotype having brown eyes.
42
Alleles - 3:1 ratio 2 Heterozygous Parents: Mothers gametes - Bb Fathers gametes - Bb (2 marks)
Offspring has 75% chance of having brown eyes + 25% chance of having blue eyes.
43
Alleles - 1:1 ratio 1 Heterozygous Parent + 1 Homozygous Parent: Mothers gametes - Bb Fathers gametes - BB (2 marks)
Offspring has 50% chance of having blue eyes + 50% chance of having brown eyes.
44
Dominant alleles in eye colour | 2 marks
Brown eyes are Dominant - B
45
Recessive alleles in eye colour | 2 marks
All eye colours except Brown eyes are recessive + especially Blue eyes - b
46
Needs to be produced to provide an accurate ratio | 1 mark
Large numbers of offspring.
47
Why do large numbers of offspring need to be produced to provide an accurate ratio? (In Punnett squares) (1 mark)
Because fertilisation is random.
48
Test (back) cross | 5 marks
Genotypes TT + Tt both produce a tall phenotype - In order to establish the genotype, a test cross is used.
49
How is a Test Cross used | 8 marks
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
Pedigree diagrams | 1 mark
Used to show how a genetic condition is inherited in a family.
51
Reason pedigree diagrams are often used | 2 marks
To advise individuals within a particular family if they are carriers of a condition.
52
Phenotype: Tall - with Heterozygous parents Genotype: (1 mark)
Tt
53
Phenotype: Tall - with Homozygous parents Genotype: (1 mark)
TT
54
Phenotype: Small - with Homozygous parents Genotype: (1 mark)
tt
55
Meiosis | 2 marks
Reduction division in a cell in which the chromosome number is halved from diploid to haploid.
56
Mucus | 2 marks
Slimy white protein, which lines the respiratory tract + alimentary canal.
57
Recessive | 2 marks
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
In males the sex chromosomes are __________. | 3 marks
Heterozygous – 1 X + 1 Y chromosome.
59
In females the sex chromosomes are ____________. | 3 marks
Homozygous – 2 X chromosomes.
60
Karyotype | 1 mark
An image of a complete set of chromosomes.
61
Meiosis forms | 2 marks
Haploid gametes (sperm + egg cells).
62
All eggs contain | 1 mark
1 X chromosome.
63
50% of sperm contain 1 __ __________ + 50% contain 1 __ __________ (2 marks)
- X Chromosome | - Y Chromosome
64
During fertilisation, there is a 50% chance that | 8 marks
- 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
Within a population there will be equal numbers of | 1 mark
Females + males.

CCEA GCSE Biology (33 decks)

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