Mendel - Genetic Inheritance

Question 1

Genetics

Answer 1

is the study of heredity in general and of genes in particular
e.g eye colour, hair colour

Question 2

Heredity

Answer 2

the passing of traits from parent to offspring (INHERITANCE)

Question 3

Phenotype

Answer 3

individual’s observable traits (such as height, eye colour, etc)

Question 4

Genotype

Answer 4

the set of genes in our DNA which are responsible for a particular trait

Question 5

traits (phenotype) are influenced by MULTIPLE genes and the environment

Answer 5

patterns of inheritance are complex and unpredictable

Question 6

A small number of traits are influenced primarily by a single gene

Answer 6

They have predictable patterns of inheritance (Mendel’s laws of heredity)

Question 7

Mendel

Answer 7

documented the mechanism of inheritance genetic in sexually reproducing organisms

Question 8

In order to study inheritance, Mendel chose to use peas:

Answer 8

> they are easy to cultivate
Available in many varieties
Produce large numbers of offspring
Strict control over the mating/breeding

Question 9

Only study traits can be OBSERVED / obvious

Answer 9

Pea colour – green vs yellow, with no other variants

Question 10

True breeding

Answer 10

When the plants self-pollinate, all their offspring are of the same variety

Question 11

Hybridisation

Answer 11

Mating, or crossing, of two varieties

Question 12

Monohybrid cross

Answer 12

A cross between two parents that breed true for different versions of a single trait

Question 13

P generation

Answer 13

True breeding parents

Question 14

F1 generation

Answer 14

(first filial) Hybrid offspring of the P generation

Question 15

F2 generation

Answer 15

(second filial) Offspring from the self-fertilisation of the F1 hybrids

Question 16

Mendel cross-pollinated two true-breeding varieties (P generations, parents), studying each trait one at a time

Answer 16

Yellow and green pea colour

Question 17

All the F1 hybrids resembled only one of their two parents (yellow peas)

Answer 17

Yellow pea was dominant

Question 18

Mendel allowed the F1 plants to self-fertilise and observed the F2 (2nd generation offspring)

Answer 18

the trait that disappeared in F1, returned
75% of the offspring had yellow peas, 25% had green peas

Question 19

inheritance of traits is governed by hereditary factors: which we now call…

Answer 19

genes

E.g. Stem height, pea colour

Question 20

These factors come in alternative versions and organisms have pairs of factor versions; called…

Answer 20

alleles

tall/dwarf, yellow/green

Question 21

An organism must inherit two copies, or alleles, of each gene

Answer 21

1 from its mother + 1 from its father

Question 22

He theorised, true-breeding parental strains, possessed a pair of identical alleles

Answer 22

• Homozygous
• Heterozygous

Question 23

Homozygous

Answer 23

An organism possessing two identical alleles for that trait (gene)
The F1 hybrid plants, on the other hand, had received two dissimilar alleles

Question 24

Heterozygous

Answer 24

An organism possessing two different alleles for that trait (gene)

Question 25

Mendel’s second postulate – Dominance/Recessiveness (2nd law)

Answer 25

The dominant allele of the gene (denoted by a capital letter, e.g. T=TALL stem) The recessive allele of the gene (denoted by a small letter, e.g. t=dwarf stem)

Question 26

The appearance, of organism depends on which versions of each allele it inherits

Answer 26

Phenotype

Question 27

What type of chart do we use?

Answer 27

Punnet chart

Question 28

In Heterozygous genotype (Tt), the dominant one dictates the organism’s phenotype Tt The stem will be tall

Answer 28

heterozygous dominance T 'wins' - more powerful

Question 29

tt

Answer 29

SHORT because two homozygous recessive alleles are present and therefore showing the phenotype

Question 30

Mendel’s third postulate – Independent Segregation

Answer 30

two copies (alleles) of each gene present in the parent separate so that each gamete receives only one allele for each trait

Question 31

During fertilisation, a sperm cell carrying one or other allele fuses with an egg cell carrying one of the alleles to produce:

Answer 31

a zygote with two alleles

Question 32

The two alleles for each trait separate (or segregate) during gamete formation and then

Answer 32

> unite at random—one from each parent—at fertilisation - In F1, half the gametes will get a yellow-pea allele and half will get a green-pea allele - Four combinations are possible in F2, explaining the 3:1 ratio

Question 33

Mendel’s Postulates - Albinism

Answer 33

The major form of albinism, Type II albinism follows the Mendel’s Law of Segregation (1 gene involved)

Question 34

Disorders that results in little or no production of the pigment melanin

Answer 34

(colour of the skin, hair and eyes)

Question 35

What is the role of the dominant allele of the gene (A)

Answer 35

encodes an enzyme involved in making melanin, the recessive one is non/low active (a)

Question 36

Alleles for Different Traits Segregate Independently

Answer 36

Mendel’s law of independent assortment states that, during gamete formation, different pairs of alleles segregate independently of one another

Question 37

Alleles that segregate independently are packaged into gametes in all possible combinations

Answer 37

4 combinations of gametes

Question 38

These gametes are allowed to combine at random to produce the F2 generation,

Answer 38

Double dominant phenotype, two single dominants and the double recessive phenotype

Question 39

What ratio is the double dominant phenotype in?

Answer 39

9:3:3:1