Genotype, Phenotype and Inheritance

Question 1

what is a genotype

Answer 1

the DNA sequence of an organism or individual which determins the specific characteristics of that organism or person

Question 2

what is phenotype

Answer 2

an organism’s observable physical and biochemical characteristics directly influenced by the genotype and /or environment.

Question 3

define gene

Answer 3

a stretch of DNA sequence at a specific chromosomal location that carries the code for the polypeptide or untranslated RNA

Question 4

what is an allele

Answer 4

a version or variant of a gene

Question 5

Non sister chromatids have

Answer 5

the same genes but different alleles

Question 6

sister chromatids have

Answer 6

identical DNA and the same alleles

Question 7

homozygous

Answer 7

2 alleles of a gene are the same

-individual is a homozygote

Question 8

heterozygous

Answer 8

two alleles of a gene are different

-individual is a heterozygote

Question 9

hemizygous

Answer 9

only one allele of a gene on the x chromosome

-makes only one copy of an x so are hemizygous for all the genes on the x chromosome only one allele

Question 10

dominant

Answer 10

the dominant allele in a heterozygote determines the phenotype

Question 11

recessive

Answer 11

the non-dominant allele in a heterozygote is called recessive

Question 12

co-dominant

Answer 12

neither allele in a heterozygot is dominant and the phenotype is new (different from the phenotypes determined by either allele)

Question 13

Autosomal recessive

Answer 13

• heterozygous unaffected
• affected individuals are homozygous recessive
• two affected individuals will only have affected offspring
• 2 heterozygous carries will have a 1/4 chance of having affected offspring

Question 14

Autosomal dominant

Answer 14

• heterozygotes affected
• autosomal dominant diseases are rarely found in homozygoes state, therefore assume that affected individuals are heterozygotes
• males and females are equally affected
• every affected individual will have at least oe affected parent
• cant skip generations

Question 15

x linked recessive

Answer 15

every affected (hemizygous) make will have at least a heterozygous carrier mother

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

affected males will have at least heterozygous daughters

whenever there are more males affected x linked recessive

Question 16

x linked dominant

Answer 16

• females affected more
• hemizygous males and heterozygous females affected
• heterozygous affected females have 50% chance of having affected offspring
• affected males cannot give trait to sons
• affected males will give trait to all daughters

Question 17

y linked

Answer 17

only males affected

affected males will give traut all sons

Question 18

an example of autosomal recessive disease

Answer 18

cystic fibrosis

Question 19

autosomal dominant disease

Answer 19

huntingtons disease

Question 20

x linked recessive disease

Answer 20

Haemophilia A

Question 21

mitochondrial

Answer 21

all individual will inherit from the mother

we get all our mitochondrial DNA from our mothers as mitochondria from sperm dont enter they are degraded

Question 22

polygenic inheritance

Answer 22

more than one gene can be involved in producing a phenotype

Question 23

linked genes

Answer 23

genes on the same chromosome
no independent assortment at meiosis
recombination frequency between 2 linked genes is dependant on the distance between the genes- more distance more chance of crossing over