Inheritance

Question 1

Genotype

Answer 1

The genetic constitution of an organism eg, all the alleles

Question 2

Phenotype

Answer 2

The expression of the genotype and its expression in the environment

Question 3

Allele

Answer 3

A specific version of the same gene

Question 4

Gene

Answer 4

Base sequence in a section of DNA that encodes for AMINO ACID SEQUENCE OF a polypeptide or functional RNA

Question 5

Locus

Answer 5

Where a particular gene is located on a pair of homologous chromosomes

Question 6

Chromosome

Answer 6

A molecule of DNA wrapped around histone proteins

Question 7

Homologous chromosomes

Answer 7

Contain the same genes at different loci, but may have different alleles

Question 8

Are homologous chromosomes the same length?

Answer 8

Yes because they have the same genes at the same loci

Question 9

Pair of Alleles at the same loci in a homologous pair do what?

Answer 9

Encode for a characteristic (based on amino acid sequence of a polypeptide chain) depending on the nature of the 2 alleles
Because they are the same gene encode for the same characteristic

Question 10

What can each allele in a homologous pair be?

Answer 10

Dominant
Recessive
Co dominant

Question 11

Dominant alleles

Answer 11

This allele will be expressed in the phenotype regardless of the nature of the other allele
Eg, will encode for the specific amino acid sequence in the polypeptide always

Question 12

Recessive alleles

Answer 12

An allele only expressed in the phenotype if the other allele (at the same locus in a homologous pair) is also recessive

Question 13

Co dominant alleles

Answer 13

When the 2different alleles in a homologous pair are both expressed in the phenotype

Question 15

Homozygous

Answer 15

When the 2alleleles in a homologous pair are the SAME eg both recessive or both dominant

Question 16

Heterozygous

Answer 16

When the 2 alleles in a homologous pair are different eg one is recessive and one is dominant

Question 17

What is a mono hybrid cross used for?

Answer 17

To breed together 2 organisms to study the inheritance of 1 particular gene

Question 18

In Gametes, how many alleles of a gene is there?

Answer 18

1 allele because in a gamete there are no homologous chromosomes, just 1 chromosome
So this chromosome will only have 1 allele for a gene

Question 19

Punnet squares

Answer 19

When 2 organisms are bred together, write both their genotypes in a cross to work out the possible genotypes offspring’s can have (and ratio of what is most likely to inherit)

Question 21

How could you prove an organism has a given genotype?

Answer 21

By using a test cross, breeding with another organism and if an offspring with a specific genotype is produced then we can work it out

Question 22

Why are the offspring produced’s genotypes not follow the ratio we calculated using punnet squares?

Answer 22

Because of random fusion of gametes, so the actual ratio of gametes is affected heavily by chance

Question 23

Punnet square of a mono hybrid cross

Answer 23

2 by 2
Studying 1 gene, only 2 alleles of each organism’s homologous chromosomes can be studied
It’s only possible to have 2 alleles of 1 gene in a homologous pair

Question 24

What is a di hybrid cross?

Answer 24

Breeding together 2 organisms to study the inheritance of alleles from 2 DIFFERENT genes

Question 26

Gametes in a dihybrid cross

Answer 26

Every gamete will have 1 allele from 1 of the genes, then 1 allele for the other gene
Because gametes don’t have homologous chromosomes so cannot have more than 1 allele of each gene

Question 27

How many possible gametes from each organism in a di hybrid cross ?

Answer 27

4 per organism
Each having 1 allele from 1 gene, and 1 allele from a DIFFERENT gene

Question 28

How many possible gametes in a mono hybrid cross?

Answer 28

2 per organism because 1 gene is studied, so it’s 1 allele in 1 gamete and the other allele of the SAME GENE in the other gamete

Question 29

Independent segregation of chromosomes

Answer 29

It is random what way the homologous chromosomes separate in meiosis, the chromosomes do not influence how each other divide
The combination of maternal and paternal chromosomes in a gamete is completely random

Question 30

Dihybrid cross punnet square

Answer 30

4 gametes possible from mother on one axis
Same for the other
=16 possible combinations of alleles for the 2GENES

Question 31

Possible genotypes in a dihybrid cross mist be written…

Answer 31

So alleles of the same gene are written together
Capital (dominant) allele first then recessive lowercase one

Question 32

Cross

Answer 32

Breed together

Question 33

How are co dominant alleles written?

Answer 33

With a capital letter to represent the same gene
Then an uppercase letter superscript to show the different allleles
ALL capital as both alleles are expressed in the phenotypen

Question 34

Can genes have more than 2 alleles?

Answer 34

Yes but in a pair of homologous chromosomes, you can only have maximum of 2 different alleles

Question 35

How are multiple alleles of the same gene written?

Answer 35

Capital letter to represent the gene
Superscript to show the different alleles

Question 36

Sex linkage

Answer 36

Genes located on a sex chromosome eg X or Y

Question 37

Sex chromosomes

Answer 37

X and Y

Question 38

Non sex chromosomes

Answer 38

Autosomes