Year 10 Genetics Revision
Name: __________________________
Terms You Should Know
Gene
Allele
DNA
Inherited
Genetics
Dominant
Recessive
Co-dominant
mutation
cloning
trait
chromosome
centromere
mitosis
meiosis
haploid
diploid
zygote
embryo
fraternal twins
karyotype
fertilisation
ovulation
gestation
progesterone
oestrogen
ovum/ova
testes
foetus
IVF
sperm
gonad
punnet square
F1
Gregor Mendel
haemophilia
thalessaemia
pedigree
homozygous
identical twins
heterozygous
continuous variation
discrete variation
sex linked
phenotype
genotype
genetic engineering
budding
vegetative propagation
amniocentesis
1. Copy and complete the following table:
Characteristic
Stem height
Stem height
Stem height
Seed colour
Seed colour
Seed colour
Seed shape
Seed shape
Seed shape
Allele 1
T (tall)
T
t
Y (yellow)
y
Y
R (round)
R
r
Allele 2
t (short)
T
t
Y (green)
y
Y
r (wrinkled)
R
r
Genotype
Tt
Phenotype
tall
Pure/Mixed
Mixed/hybrid
YY
yellow
pure
2. In Mendel’s experiments with pea plants, pure yellow seeds (YY) were crossed with pure
green seeds (yy). Draw a punnet square or checkerboard to show why all the first generation
(F1) plants had yellow seeds. Show why the F2 plants were ¾ yellow seeded and ¼ were green
seeded.
3. (a) If R represents the allele for a round seed and the r allele gives wrinkled seeds, which of the
genotypes Rr, RR and rr represents
(i) homozygous round seed
(ii) heterozygous round seed
(iii) homozygous wrinkled seed ?
(b) is it possible to get a heterozygous wrinkled seed ? Explain.
4. A particular species of plants can have red or white flowers. Red is the dominant gene.
(i)
Pure red flowered plants are crossed with hybrid (mixed) red flowered plants. What
% of the F1 offspring would be red ?
(ii)
If RR plants are crossed with rr plants, what % of the F1 would be red ? What %
would be white ?
(iii)
If 2 heterozygous red flowered plants are crossed, what would be the ratio of red
flowered offspring to white flowered offspring ?
5. Albinism is a hereditary condition where skin pigments are not formed. Normal skin
pigmentation (P) dominates over albinism (p)
(i)
What are the possible genotypes for a person with normal skin pigmentation ?
(ii)
What are the possible genotypes for a person with albinism ?
(iii)
If the first child of a couple with normal phenotypes is an albino, what are the
chances that their second child will also be an albino ?
6. Name 5 human traits.
7. How many genes do you have for each trait ?
8. In order to show a recessive trait like blue eyes, what would your genotype be ?
9. Describe the structure of DNA. How do the bases join ?
10. Give 3 examples of genetic engineering ?
11. Humans have _______ chromosomes in ________ pairs.
12. How many chromosomes are found in gametes ? Why ? Name the process that makes gametes.
13. Describe how fraternal twins are related ?
14. What happens in cell division in body cells ? Name this process.
15. What is the difference between genotypes and phenotype ?
16. Draw your family’s pedigree for eye colour (grandparents, parents, you, your siblings)
17. Explain how DNA, chromosomes and genes are related ?
18. Draw a punnet square to show the cross between a sufferer of Huntington’s Disease with a
normal person. The gene for Huntington’s is dominant (H), over the recessive (h) gene.
19. What does variation mean ?
20. A pedigree chart showing the inheritance of the dominant Huntington’s allele.
1
3
2
4
7
5
8
6
9 99
10
11
13
Have Huntington’s
Male
(a)
(b)
(c)
(d)
Female
How many grandchildren do 1 and 2 have ?
What is the genotype and phenotype of 2,5,9 and 7 ?
What is the probability that the next child of 11 and 12 has the disease ?
What percentage of female family members have the disease ?
12
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