15 genetics

Question 1

what’s a gene

Answer 1

A gene is that part of the DNA molecule
which codes for one polypeptide

Question 2

what’s an allele

Answer 2

An allele is a particular gene coding for
a specific character

Question 3

what are the sources of different alleles of a gene

Answer 3

Gene mutations

Question 4

the changes in the sequence of base pairs in part of a DNA molecule coding for a polypeptide can be one of four types

Answer 4

• Substitution of one or more base pairs by others
• Addition of one or more base pairs
• Deletion of one or more base pairs
• Inversion where a particular nucleotide sequence is reversed

Question 5

Causes of mutations

Answer 5

They are caused by a number of
chemicals, high energy radiation
e.g. X rays, gamma rays and
ultraviolet light.

Question 6

what is A mutagen

Answer 6

A mutagen is an agent which
causes a mutation

Question 7

what are considers Chromosome mutations

Answer 7

include changes in chromosome structure which can happen during division

Question 8

types of Chromosome mutations

Answer 8

1-duplicated
2-Break off and be lost
3-Break off and rejoin with the sequence of genes inverted
4-Break off and attach to another chromosome

Question 9

The transfer of a portion of one chromosome to another is called

Answer 9

translocation

Question 10

what is Chromosome mutations

Answer 10

Changes in chromosome number result from unequal separation of chromosomes between daughter cells during division

Question 11

what is non-disjunction

Answer 11

After meiosis, one daughter cell may lack one chromosome and the other have one extra chromosome

Question 12

Chromosomes are present in homologous pairs in

Answer 12

somatic cells

Question 13

Chromosomes are present in homologous pairs in

Answer 13

somatic cells

Question 14

There are at least how many alleles for each character

Answer 14

There are at least 2 alleles for each character

Question 15

A recessive character will only be expressed if

Answer 15

if both alleles are recessive

Question 16

what does A dominant allele mask

Answer 16

A dominant allele masks the expression of a recessive allele

Question 16

what does A dominant allele mask

Answer 16

A dominant allele masks the expression of a recessive allele

Question 17

what is The genotype

Answer 17

The genotype is the genetic constitution expressed in terms of its genes.

Question 18

what is The phenotype

Answer 18

The phenotype is the observable features that arise from its genetic constitution

Question 19

what is A monohybrid cross

Answer 19

A monohybrid cross involves a single character that is controlled by one gene with two or more alleles.

Question 20

Homozygous =

Answer 20

= Pure (Homogeneous)

Question 21

what is Pure Dominant

Answer 21

the individual only has genes for the dominant trait.

Question 22

what is Pure Recessive

Answer 22

the individual only has genes for the recessive trait.

Question 23

Heterozygous =

Answer 23

Mixed (Heterogeneous)

Question 24

what is A heterozygous

Answer 24

an individual has one dominant gene and one recessive gene for a trait. The result is the dominant gene is the one expressed or shown.

Question 25

in Autosomal dominant The mutated gene is

Answer 25

a dominant gene and One copy of the gene is
sufficient to have the trait

Question 26

Autosomal recessive functions

Answer 26

• Two copies of the gene are
  necessary to have the trait
• Typically not seen in every
  generation of an affected family

Question 27

what is Brachydactyly

Answer 27

its an Autosomal dominant disease and it is a rare condition of humans in which the fingers are very short It is due to a mutation in the gene for finger length tends to occur in members of every generation

Question 28

what is Albinism

Answer 28

Albinism is a rare inherited condition in which the individual has a block in the biochemical pathway by which the pigment melanin is formed. * Albinos have white hair, very light coloured skin and pink eyes * It shows an autosomal recessive inheritance * It often skips one or more generations altogether

Question 29

what is Cystic fibrosis

Answer 29

its An autosomal recessive trait that
affects the lungs and digestive system.
The body produces thick and sticky
mucus that can clog the lungs and
obstruct the pancreas.

Question 30

The red blood cell antigen is coded
for by

Answer 30

by the gene I (for isohaemaglutinogen), which has three alleles IA, IB and IO.
A and IB are codominant, while IO is
recessive.

Question 31

what is Sickle cell anaemia

Answer 31

• Sickle cell anaemia is a genetic disease in the haemoglobin of the red blood cells
  The sickle cell allele causes
  haemoglobin to form a long
  strands
• The red blood cell carrying
  these molecules distorts into
  a long sickle shape

Question 32

The shape of the haemoglobin molecule is controlled by two alleles

Answer 32

Normal Haemoglobin allele (HbA)
* Sickle Cell Haemoglobin allele (HbS
)

Question 33

The genetics of sickle cell anaemia The three phenotype produced are:

Answer 33

1. Normal
   * Normal individuals have two normal haemoglobin alleles
2. Sickle cell anaemia
   * Sickle cell anaemia patients have two sickle cell alleles in their genotype
3. Sickle cell trait - 50% of the haemoglobin is affected.
   * Sickle cell trait individuals are heterozygotes, having one of each allele

Question 34

Normal haemoglobin allele is —-
* Sickle cell allele is —-

Answer 34

Normal haemoglobin allele is HbA
* Sickle cell allele is HbS

Question 35

Genotypes Phenotypes
HbAHbA ———-
HbAHbS ———
HbSHbS ———-

Answer 35

Genotypes Phenotypes
HbAHbA Normal haemoglobin
HbAHbS Sickle cell trait
HbSHbS Sickle cell anaemia

Question 36

Sex is determined by

Answer 36

by the sex chromosomes (X and Y)

Question 37

Colorblindness is a recessive and

Answer 37

and X-linked trait (Xb). The allele for normal vision is dominant and is represented by XB

Question 38

why The presence of many affected individuals in a family does not always mean that the trait is dominant.

Answer 38

because A trait may be recessive but still show up in all generations of a pedigree.