Human and Animal Genetics

Question 1

Human Chromosomes

Answer 1

Human chromosomes
22 similar
AUTOSOMES
(non=sex
chromosomes
1 pair of sex
chromosomes
Female XX
Male XY

Question 2

Karyotype

Answer 2

arrangement of
chromosomes (the number of
chromosomes and their types )
* Diploid chromosomes = 2 copies of
each chromosome
* haploid chromosomes = 1 copy of
each chromosome

Question 3

Structure of Chromosomes

Answer 3

DNA
Long Arm
Centromere
Short arm

Question 4

Ploidy – the number of each
chromosome

Answer 4

*Diploid = 2n (most cells)
*Haploid = n (the gametes: sperm and egg)
*Polyploid = many copies (e.g. some tomato
plants are tetraploid (4n); wheat is
hexaploidy(6n))

Question 5

Genetics – Mendelian Inheritance

Answer 5

Phenotypes:
* Round Shells
* Wrinkled Shells
HE CROSSED THESE

Question 6

||

Answer 6

Each parent is diploid – so
there are two copies of each
chromosome.

Question 7

R||R

Answer 7

The R represents the gene
that produces the “round
shell phenotype”. This is
known as an ALLELE. There
are two alleles, one on each
chromosome.

Question 8

r||r

Answer 8

The “r” represents an
alternative allele the gene
that produces the “wrinkled
shell phenotype”. There are
also two copies of this allele,
one on each chromosome

Question 9

Gametes Fuse

Answer 9

one from
each parent to form the
Zygote or fertilised egg. Each
combination is possible

Question 10

F1

Answer 10

ALL ROUNDS R||r

Question 11

F1 Cross

Answer 11

F2
RR,Rr,Rr,rr
3:1
round:wrinkled

Question 12

Locus

Answer 12

position on the chromosome

Question 13

Alleles

Answer 13

variants of the same gene or locus
* E.g. “R” or “r”

Question 14

Homozygous

Answer 14

same alleles (e.g. “RR” or “rr”)

Question 15

Heterozygous

Answer 15

different alleles (e.g. “Rr”)

Question 16

Co Dominance

Answer 16

*Some alleles are neither dominant nor recessive
*These are known as co-dominant alleles – both
contribute to the phenotype

Question 17

sex-linked inheritance

Answer 17

Some gene loci are found on the sex chromosomes (X
and Y chromosome)

Question 18

X- chromosome inactivation

Answer 18

*Males have one X-
chromosome
*Females have 2 X-
chromosomes
*In females one of the X
chromosomes is inactivated
*Random process

Question 19

Linked genes

Answer 19

SAME chromosmes

Question 20

Unlinked genes

Answer 20

different
chromosomes

Question 21

Genetic Abberations

Answer 21

*Sometimes things go wrong
*Usually occurs at meiosis
*The production of gametes with the wrong
numbers of chromosomes

Question 22

Genetic Recombination

Answer 22

*Occurs in linked genes
*Occurs at meiosis
*One of the most important mechanisms
that generates variability within a species
*Provides the variation for natural selection
to act upon