Lecture 7 and 8

Question 1

What is the theory of pangensis?

Answer 1

Seeds are produced by all body parts, collected in reproductive organs and transmitted to offspring

Question 2

Who proposed the theory of pangenesis?

Answer 2

Hippocrates (400B.C.)

Question 3

What is the theory of preformationism?

Answer 3

Sex cells contain fully developed homunculus (mini human)

Question 4

What were the two theories surrounding preformationism?

Answer 4

Spermists: homunculus found in sperm
Ovists: homunculus resides in egg

Question 5

What is the blending theory of inheritence?

Answer 5

Hereditary traits are malleable, blending together through generations

Question 6

What plant did Mendel work with?

Answer 6

Peas: Pisum satvium

Question 7

Why peas?

Answer 7

Easy to handle, grow well, self fertilise or cross fertilise, short generation time, lots of offspring, discrete traits, pure bred strains exist

Question 8

What were the basic ratios in Mendel’s experiments:

Answer 8

F1: all the same
F2: 3:1 ratio

Question 9

What did Mendel’s data suggest?

Answer 9

Particulate theory of inheritance

Question 10

What is Mendel’s first law?

Answer 10

Law of segregation

Question 11

What is the law of segregation?

Answer 11

Two factors for each trait separate during gamete formation and unite at random at fertilization

Question 12

What was Mendel’s experiments involving more then one phenotype called?

Answer 12

Dihybrid cross

Question 13

What is Mendel’s second law?

Answer 13

The law of independent assortment

Question 14

What is the law of independent assortment?

Answer 14

During gamete formation, different pairs of alleles segregate independently of each other

Question 15

What enzyme causes wrinkled peas?

Answer 15

Starch branching enzyme 1 (Sbe1)

Question 16

What enzyme causes green phenotype?

Answer 16

Lack of an enzyme that breaks down Chlorophyll called stay green (Sgr)

Question 17

How are family genetics analysed?

Answer 17

Pedigree analysis

Question 18

What are 2 features of dominant diseases?

Answer 18

• Affected individuals have affected parent

- Doesn’t skip generations

Question 19

Give an example of a dominant disease in humans.

Answer 19

Huntington’s disease (progressive death of nerve cells)

Question 20

What is the inheritence of dominant disease also called?

Answer 20

Vertical transmission

Question 21

What is the mechanism for huntingtons?

Answer 21

Httex1 gene variant produces abnormally folded proteins

Question 22

Why do misfolded Httex1 genes cause huntingtons?

Answer 22

Protein accumulates in neurons causing damage over time

Question 23

What are features of recessive diseases?

Answer 23

Affected indivduals parents not always affected (skips generations)
Seen more in consanguineous matings

Question 24

Give an example of recessive disease in humans.

Answer 24

Cystic fibrosis

Question 25

What type of transmission are recessive disease?

Answer 25

Horizontal

Question 26

What is the most common non-functional varient of CFTR?

Answer 26

delta F508 (deleted amino acid at position 508)

Question 27

Snapdragons show variance from Mendel's first law because...

Answer 27

Incomplete dominance: F2 gives 1:2:1 red:pink:white

Question 28

Lentils giving rise to spotted/dotted phenotype not seen in F1 generation is known as...

Answer 28

Co-dominance

Question 29

How many genotypes and phenotypes are there for blood groups?

Answer 29

6 and 4

Question 30

Why are blood groups this way?

Answer 30

More than one allele at a locus

Question 31

Why do dominance series exist?

Answer 31

There are dominance heirachys

Question 32

Give an example of a dominance series in mammals.

Answer 32

Agouti locus: Coat colour in mouse, wild type allele produces fur with yellow and black bands

Question 33

One gene can act on multiple systems or tissues. This is called...

Answer 33

Pleiotrophy

Question 34

Give an example of pleiotriophy in mice.

Answer 34

One Ay locus produces yellow coat colour, | Two Ay are not born (genotype is lethal)

Question 35

What is epistasis?

Answer 35

The interaction of genes that are not alleles (e.g. supression of the effect of one such gene by another)

Question 36

What are two key concepts when considering environment interactions of genes?

Answer 36

Penetrance and expressivity

Question 37

What is penetrance?

Answer 37

Proportion of a population with a genotype that have the phenotype

Question 38

What is expressivity?

Answer 38

The degree or intensity with which a particular genotype is expressed in a phenotype

Question 39

Give an example of expressivity

Answer 39

Siamese cats (same genotype, fur colour different), temperature sensitive gene for melanin

Question 40

Give an example of penetrance.

Answer 40

Phenylketonuria (PKU)

Question 41

What is phenylketonuria?

Answer 41

Recessive disease, mutation in phenlyalanine hydroylase, unable to metabolose phenylalanine which becomes toxic

Question 42

Why is phenlyketonuria an example of penetrance?

Answer 42

Phenotype changes depending on diet

Question 43

Who first demonstrated polygenetic inheritance?

Answer 43

Karl Pearson (1903), height is correlated in families