D3.2 - monohybrid inheritance (5k-m)

Question 1

why are flowering plants, such as peas, well-suited to study inheritance?

Answer 1

• produce male and female gametes on the same plant, allowing self-pollination and self-fertilization
• pollination is essential for carrying out a cross because pollen contains male gametes and female gametes are located in the ovary

Question 2

how are flowering techniques used commercially?

Answer 2

genetic crosses are widely used to breed new varieties of crop or ornamental plants

Question 3

why are flowering plants well suited to study inheritance over multiple generations?

Answer 3

the relative ease with which pollination can be controlled means multiple generations of plant inheritance can be studied

Question 4

what is the P generation?

Answer 4

P generation - parental generations, with only pure-breeding individuals (homozygtes)

Question 5

what is the F1 generation?

Answer 5

F1 generation - offspring of the cross between individuals in the P generations

Question 6

what is the F2 generation?

Answer 6

F2 - offspring resulting from the cross between two individuals of the F1 generations.

Question 7

what is a dominant allele?

Answer 7

allele that is always expressed in the phenotype
- it can be a homozygous dominant genotype (AA) or a heterozygous genotype (Aa) and it will produce the same phenotype as they contain the dominant allele

Question 8

what is a recessive allele?

Answer 8

allele that is expressed if no dominant allele is present.
(aa)

Question 9

what is a Punnett grid?

Answer 9

a diagram used to show how alleles within an individuals genotype are split into gametes, plus the combination of alleles that could occur in the genotype of the offspring

Question 10

what is phenylketonuria?

Answer 10

recessive genetic condition caused by a mutation in an autosomal gene that codes for the enzymes needed to convert amino acid phenylalanine to the amino acid tyrosine.
- people with PKU must restrict the amount of protein they consume, otherwise the phenylalanine levels can become toxic and impair brain development.

Question 11

what is inductive reasoning?

Answer 11

inductive reasoning occurs when scientists base a theory on observations of some but not all cases, allowing for the possibility that the conclusion could be false

Question 12

what is deductive reasoning?

Answer 12

deductive reasoning occurs when we apply established knowledge to explain an observation

Question 13

how can we identify recessive traits in a pedigree chart?

Answer 13

if the characteristic is recessive, two parents without the characteristic can have a child with the characteristic

Question 14

how can we identify dominant traits in a pedigree chart?

Answer 14

if the characteristic is dominant, two parents with the characteristic can have a child without the characteristic

Question 15

why do many societies prohibit marriage between close relatives based on the pedigree chart analysis?

Answer 15

• most genetic disorders are rare in the general population, but more common within closely related family groups.
• permitting breeding between close relatives would further increase the frequency of people with the genetic disorder.

Question 16

what is incomplete dominance?

Answer 16

incomplete dominance is when a heterozygous will have an intermediate phenotype

Question 17

what is an example of incomplete dominance inheritance?

Answer 17

mirabilis jalapa has multiple pure breeding alleles controlling flower colour through pigment production
- in a heterozygous, both of the pigments will be produced and the plant will appear as an intermediate colour
- for example, CrCw denotes a plant expressing both the red and white pigment and therefore appears pink

Question 18

what is codominance?

Answer 18

codominance is when a heterozygote has a dual phenotype

Question 19

what is an example of codominance?

Answer 19

AB red blood cells will bind to the same antibodies as both type A red blood cells and type B red blood cells

Question 20

what is a pedigree chart?

Answer 20

shows a record of ancestry and so appears as a family tree with symbols representing individuals phenotype and sex
- squares representing males and circles representing females
- filled shapes represent the presence of a characteristic and empty shells represent the lack of a characteristic

Question 21

how could we determine whether a characteristic could be sex linked or is caused by an autosomal gene?

Answer 21

1. determine whether the characteristic is caused by a dominant or recessive allele
2. look for one of the following patterns of inheritance that would disprove sex-linked inheritance, and indicate autosomal inheritance

Question 22

how can we determine whether a characteristic is recessive for determination of sex or autosomal genes for a daughter?

Answer 22

if a characteristic is recessive, the daughter must have inherited a recessive allele from both parents
- if her father has a dominant phenotype the allele cannot be sex-linked
- dad + daughter –> recessive

Question 23

how can we determine whether a characteristic is recessive for determination of sex or autosomal genes for a son?

Answer 23

if the characteristic is dominant, the son must have inherited a dominant allele from his mother (and Y chromosomes from the father)
- so if his mother has the recessive phenotype, the alleles cannot be sex-linked
- son + mom –> dominant

Question 24

what is the relationship between number of alleles for a gene and the phenotypes produced?

Answer 24

although an individual can only have two alleles for each gene, the populations gene pool may contain alleles for a given gene
- this increases the number of phenotypes in a population, as each allele may be dominant, recessive incompletely dominant or co-dominant to another allele

Question 25

what is the inheritance of ABO blood groups, and what type of inheritance is shown?

Answer 25

ABO blood groups is an example of multiple alleles inheritance and there are 3 alleles:
Ia - produces A-type antigens on the surface of red blood cells.

Ib - produces B-type antigens on the surface of red blood cells.

I - doesn’t produce any antigens on the surface of red blood cells.

Question 26

what are the 6 types of genotype for ABO blood groups?

Answer 26

IaIa / Iai - blood group A

IbIb / Ibi - blood group B

IaIb - blood group AB

ii - blood group O

Question 27

what are the 4 types of phenotype for ABO blood groups?

Answer 27

Ia and Ib are dominant to I as there is no difference in phenotype for the homozygous dominant and heterozygous individuals.
Ia and Ib are codominant because when they are present together within a heterozygote, both the A antigen and B antigen are expressed om red blood cells, giving a dual phenotype.

Question 28

how is codiminance different to incomplete dominance?

Answer 28

how the heterozygous phenotypes manifest differs:
- in codominance, both individual phenotypes (due to each allele can be identified) in what is called a dual phenotype - AB red blood cells nind to the same antibodies as type A and B red blood cells.
- in incomplete dominance, an intermediate phenotype is produced due to mixing of the product of each allele:
mirabilis jalapa appears pink due to the mixing of the red and white pigments produced by the 2 alleles.

Question 29

what are the 2 sets of sex chromosomes?

Answer 29

the human population has 2 sets of chromosomes: X and Y

XX - female

XY - male

Question 30

what are sex-linked genes?

Answer 30

sex-linked genes are the genes located only on the X chromosome

Question 31

why is it important to know whether the males gamete contains an X or Y chromosome when predicting inheritance of genes that are located on the C chromosome?

Answer 31

far more genes are carried by the X chromosome than the Y chromosome

Question 32

what is haemophilia?

Answer 32

a disorder in which blood does not clot properly and is an example of a sex-linked genetic disorder, caused by a recessive allele.

there are 2 alleles, which are found on the X chromosome:
- XH - no haemophilia
- Xh - haemophilia
- Y - used to indicate the Y chromosome, which does not have the locus for the haemophilia gene