L17- genotype, phenotype and inheritance

Question 1

central dogma

Answer 1

Question 2

genotype

Answer 2

our set of genes

Question 3

phenotype

Answer 3

our traits- proteins

Question 4

what factors influence our phenotype

Answer 4

• e.g. Genetic disorders like CF (genetic mechanism)
• infection (environment)
• non commiunicable disease (genotype and environment)

Question 5

what is a gene

Answer 5

A sequence of DNA found at a specific location within chromosomes, which codes for a protein.

Question 6

an allele is a

Answer 6

form of a gene

Question 7

how many genes do we have

Answer 7

25,000

• all indiviudals have two copies of each given gene ( one maternala nd one paternal)

Question 9

many alleles of a gene

Answer 9

within a population e.g. why we have different hair and eye colours

• gene codes of hair colour
• allele codes for the specific colour

Question 10

homozygous

Answer 10

tow alleles of a gene are the same

Question 11

heterozygous

Answer 11

two alleles of a gene are different

Question 12

hemizygous

Answer 12

only one allele of a gene on the X chromosome (male only)

Question 14

dominant

Answer 14

a dominant alleles in a heterozygote determines phenotype (Aa – would have A phenotype)

Question 15

recessive

Answer 15

the non-dominant allele in a heterozygote is called recessive.

Question 16

co- dominance

Answer 16

where both alleles have equal contribution to phenotype e.g. ABO blood types

Question 17

co-dominance and ABO blood groups

Answer 17

Human isoglutamin gene codes for glycoproteins on the surface of RBC.

Three alleles for blood type:

• A or I^A
• B or I^B
• O or I^O

We have 2 alleles each

• Allele A is dominant over O
• Allele B is dominant over allele O
• Neither A or B is dominant over the other= Co-dominant

Question 18

in a pedigree each line represents

Answer 18

a separate generation

Question 19

oldest sibling on the pedigree will be

Answer 19

furthest to the left

Question 20

how to draw a pedigree- reminder of symbols

Answer 20

Question 21

describe III.17

Answer 21

youngest of 8 children, married with no children

Question 22

in autosomal recessive disorders, heteozygotes will be

Answer 22

unaffected

Question 23

in autososmal recessive disorders males and females

Answer 23

equally affects

Question 24

in autososmal recessive disorders, if both parents are heterozygotes

Answer 24

Two heterozygotes have 25% chance of having affected offspring

Question 25

with autosomal recessive disordrrs, 2 affected homozygous individuals will have

Answer 25

affected offspring only

Question 26

heterozygous pedigree characteristic

Answer 26

isease comes out of nowhere (disease skip generations). Both parents of the affected must be heterozygous ‘carriers’ e.g. CF

Question 27

in autosomal domiannt disorders heterozygotes will be

Answer 27

affected

Question 28

in autosomal dominant disorders male and females are

Answer 28

equally affected

Question 29

autosomal domiannt disorders are rarely found

Answer 29

in homozygous state

• if you see individual with disease, assume they are heterozygous

Question 30

every individual with autosomal dominant disorder in heterozygous form

Answer 30

has a 50% chance of haveing affected off spring

e.g. huntingtons disease

Question 31

characteristic of autosomal domiannt pedigree

Answer 31

will not skip generations

• every affected indiivudal will have at lest one affected parent

Question 32

who are affected with X-linked recessive disorders

Answer 32

Hemizygous men and homozygous females are affected.

Question 33

X-linked recessive disorders always more common in

Answer 33

males

Question 34

heterozygous female carrier has a

Answer 34

50% chance of havign an affected son

Question 35

man with x-linekd recessive disorder cannot

Answer 35

cannot give trait to sons (only get Y chromosomes from dad)

E.g. Haemophilia

Question 36

x-linked recessive pedigree

Answer 36

Son is hemizygous recessive

Every affected male will have a heterozygous carrier mother

Every affected female will have an affected father and a carrier mother

Question 37

show an x-linked recessive punnet square example for haemophilia

Answer 37

no H gene on the Y chromosome

Question 38

in X-linked dominant disorders men and women

Answer 38

affected

• hemizyous males
• heterozygous females

Question 39

in x-linked dominant diseases females have a ….. chance of havign affected offspring

Answer 39

50%

Question 40

in X-linked dominant disroders, affecrted males cannot give traits to sons, but will

Answer 40

give it to all their daughters e.g. fragile X syndrome

Question 41

Y linked disorders only occur in

Answer 41

males

• appearin all sons of males who exhibit that trait
• absent in daughters of trait carriers (pehnotypically normal)
  e. g. male infertility

Question 42

mitochondrial inhertiance occurs due to

Answer 42

mitochodria having separate DNA (mDNA)

Question 43

mDNA is inherited from

Answer 43

mother due to sperm mitochondria not entering the egg.

Question 44

polygenic/ complex or multifactorial inheritance shows that

• give an example

Answer 44

More than one gene can be involved in producing a phenotype

e.g. albinism

Question 45

Albinism is inherited in a recessive manner- monogenic or polygenic?

• monogenic

Answer 45

(Albinisms is inherited in a recessive manor)

One gene: Gene A: Two alleles: A, a

You would expect all offspring to be albino…. HOWEVER in real life non of the offspring are affected.

Question 46

Albinism is inherited in a recessive manner- monogenic or polygenic?

• polygenic

Answer 46

Two genes: Gene A1 (A1,a1) and A2 (A2, a2)

Question 47

genes on the same chromosome are said to be

Answer 47

linked

Question 48

genes on different chormsosmes are said to be

Answer 48

not linked

Question 49

linked genes do not show

Answer 49

independent assortment at meiosis

Question 50

what can occur to linked chromosomes

Answer 50

crossing over

Question 51

linked chromsosmes can show corssinging over in prophase, producing

Answer 51

new combinations of zygotes

Question 52

recombination frequency in linked chromosomes depens on

Answer 52

the distance between the two linked genes

• Genes closely together are ‘tightly linked’
• Genes far apart on the same chromosome behave as unlinked genes

Question 53

which linked genes are more likely to cross over

Answer 53

e. g. A and E much more likely to cross over than A and D or E and D.
- closer together