Basic Mendelism

Question 1

Lamarckism

Answer 1

(Acquired characteristics) -e.g a blacksmith would build muscle which they would then pass on to their offspring

Question 2

Mendel’s first experiment

Answer 2

• Yellow x Green (P1, Parental generation): all offspring Yellow (F1, first filial generation).
• An important result - not blended, but one character hidden. Self-fertilise these; ratio of 3 yellow: 1 green in second generation. Remarkable
• green reappears in predictable frequency

Question 3

What is the interpretation of Mendel’s first experiment?

Answer 3

• genes are particles that are bearing information
• this information can be concealed but it is still present
• each pure line - two copies of the particle for colour
• pollen and egg both receive one copy each - fertilised egg one green and one yellow
• the Y allele is dominant to the recessive G allele

Question 4

Genetic Cross for Mendel’s first F1 Cross

Answer 4

Y G

Y YY YG

G YG GG

Question 5

Gamete

Answer 5

Sperm or egg; a single set of genetic instructions; a haploid cell

Question 6

Zygote

Answer 6

The fertilised egg and all body cells; a double set of genetic instructions in a diploid cell

Question 7

Locus

Answer 7

The chromosomal location of a genetic instruction; e.g. the locus for the ABO blood group

Question 8

Allele

Answer 8

Alternative forms at a particular locus – the allele for A, B, or O blood group

Question 9

Homozygote

Answer 9

Two identical copies of an allele – an AA, BB or OO

Question 10

Heterozygote

Answer 10

Non-identical copies of an allele – an AB, AO or BO

Question 11

Phenotype

Answer 11

Physical appearance of an individual with a particular genotype – blood group O

Question 12

Genotype

Answer 12

Genetic constitution that underlies the phenotype – AA, BB, OO, AB, AO or BO

Question 13

Dominant

Answer 13

An allele that in a heterozygote masks the effects of the the other allele - A and B alleles

Question 14

Recessive

Answer 14

An allele that in a heterozygote has its effects masked by other allele and is only expressed in the homozygote - O allele

Question 15

Mendel’s first law

Answer 15

The two members of a gene pair segregate into separate gametes; half carrying one member of the pair and the other half the other member

Question 16

Symbols in human pedigree

Question 17

Dominant inheritance (Brachydactyly)

Answer 17

• (short hands and stubby fingers)
• Unaffected parents only have unaffected children
• Does not skip generations: every effected individual has an effected parent
• Within families with one affected parent about half of the children are affected

Homozygotes for the Brachydactyly allele die early in childhood

Question 18

Huntingtons disease and dominant inheritance

Answer 18

• ( Hapsburg Lip in Philip IV of Spain )
• Follows dominant pattern
• It is associated with age related loss of neurons in the brain and memory loss
• first autosomal loci in humans to be mapped by Nancy Wexler

Question 19

Recessive inheritance

Answer 19

• Affected individuals may have unaffected parents
• Skips generations (about one child in four in and affected family has the condition)
• An affected child must be homozygous recessive (aa) and its parents must be heterozygous (Aa)

Question 20

Cystic fibrosis (recessive inheritance)

Answer 20

• Failure to transport protein that moves liquids across cell membranes; lungs get clogged up with mucus
• In European populations, 1/25 individuals are carriers to the sky tic fibrosis allele