Question

Question 2 0.5 points Save As Suppose that in plants, smooth seeds (5) is dominant to wrinkled seeds (s), and tall plants () is dominant to short plants (t). An F1 plant from a mating between homozygous plants that were tall/smooth and short/wrinkled was crossed to the short/wrinkled parent. What proportion of the progeny is homozygous for short and wrinkled alleles? 1/2 1/4 1/8 1/16 O 00 A

Answer 1

2) it is specified that the parents are homozygous

• hence the parents are TTSS and ttss
• gametes are TS, TS and ts , ts
• F1 generation becomes TtSs and TtSs (1:1:1:1)
• so all of them are the same genotype TtSs we cross with ttss (short wrinkled, since it is recessive it must be homozygous)
• TtSs vs ttss

• 	ts	ts	ts	ts
  TS	TtsS	TtSs	TtSs	TtSs
  Ts	Ttss	Ttss	Ttss	Ttss
  TS	TtSs	TtSs	TtSs	TtSs
  ts	tsts	tsts	tsts	tsts

  
  
• Hence tsts is homozygous and short and wrinkled hence 4 offspring out of 16, that is 1/4

3)The recessive lethal allele must be homozygous for it to be lethal

if s is the lethal allele

Ss vs Ss

	S	s
S	SS	Ss
s	Ss	ss

one in 4 is dead

so the ratio is 3:1, 3 viable one dead.

4) and) duplication of a segment of chromosome 21

The down disease is a genetic condition associated with abnormal cell division tend to result in a child born with an extra copy or portion of chromosome 21. This mutation causes the developmental patterns and physical traits of down ’s syndrome.

Hence it is also called trisomy 21.

5) we need more information because

the order could be

ABC or CAB so we need more information to find out the actual distance

6) The reciprocal cross is used to determine the role of gender in phenotypes

for example crossing a male donkey and female horse produces a hinny, and male horse and female donkey produces a mule

so mendel performed it to determine whether the inheritance of a trail is determined by the parent who carries it.