Lab 6: Genetic Crosses Name: ________________________ Lab section: _

ID: 69189 • Letter: L

Question

Lab 6: Genetic Crosses Name: ______________________________ Lab section: ____________ Lab Instructors name: _____________________ Last 4 digits of your CUNYFirst Empl ID #: _____5250________ Fall 2014 Read Chapter 7 and print out the sample genetic cross posted below the lab on the portal, to use as a guide. Below is a list of the phenotypes used in this lab. These are all single gene traits that show complete dominance. Use this information to set up and analyze your crosses. Trait Dominant phenotype Recessive Phenotype Flower color Purple flowers White flowers Plant Height Tall plants Short Plants Seed Shape Smooth seeds Wrinkled seeds Seed Color Yellow seeds Green seeds Part I: Symbols and definitions: 1. a) What is an allele? What is a gene? Give an example of 2 alleles of a human gene. (0.5 pts) b) What is the difference between an organism that is a homozygote and one that is a heterozygote? (0.25 pts) c) What is the difference between an organisms genotype and its phenotype? (0.25 pts) 2. For each trait in the table below, indicate ALL OF THE GENOTYPES that are possible. Use the first letter of the dominant trait to indicate the trait. (2pts) Trait Dominant genotype(s) Recessive genotype(s) Flower color Purple = White = Plant Height Tall = Short = Seed Shape Smooth = Wrinkled = Seed Color Yellow = Green Pick three of the crosses to complete using any 3 of the last 4 digits of your CUNYFirst BC student Empl ID. If there are repeats, pick random numbers, so you are doing 3 different crosses. Circle the numbers of the crosses you are doing in column 1 below. You must pick 3 different crosses. If there are multiple repeated numbers in your ID, pick additional numbers of your choice. Cross Number Male parent traits Female parent traits 0 Heterozygous for flower color Heterozygous for height Homozygous dominant for flower color Heterozygous for height 1 Heterozygous for flower color Homozygous dominant for height Heterozygous for flower color Homozygous dominant for height 2 Heterozygous for flower color Heterozygous for seed color Heterozygous for flower color Heterozygous for seed color 3 Homozygous recessive for flower color Heterozygous for seed color Homozygous dominant for flower color Heterozygous for seed color 4 Homozygous recessive for seed shape Homozygous recessive for height Heterozygous for seed shape Heterozygous for height 5 Heterozygous for seed shape Heterozygous for height Heterozygous for seed shape Homozygous recessive for height 6 Homozygous dominant for flower color Homozygous recessive for seed shape Homozygous recessive for flower color Homozygous dominant for seed shape 7 Heterozygous for flower color Homozygous recessive for seed shape Heterozygous for flower color Homozygous recessive for seed shape 8 Heterozygous for seed shape Heterozygous for seed color Homozygous recessive for seed shape Homozygous dominant for seed color 9 Heterozygous for seed shape Homozygous recessive for seed color Homozygous recessive for seed shape Homozygous recessive for seed color Now you can use the charts and Punnett squares on each of the following pages to complete your crosses. You can use the sample of a genetic cross posted on the BioPortal directly below the lab for a guide in doing these crosses. Cross 1: Please write the number of the cross you are performing: ______________ Then fill in the genotype and phenotype for each parent below. Use the sample of a genetic cross posted on the portal directly below the lab for a guide. Sex Genotype Phenotype Male Female Step 1: Determine the different gamete combinations that each parent can contribute to the offspring. Check the hint from the sample problem when you are doing this. Sex Gamete 1 Gamete 2 Gamete 3 Gamete 4 Male Female Step 2: Fill in the Punnett Square below Male gametes place across ? Female Gametes: Place below: ? Step 3: Find the Phenotype of each of the 16 combinations in your Punnett Square page. Phenotype youve found in offspring Number of offspring with this phenotype Cross 2: Please write the number of the cross you are performing: ______________ Then fill in the genotype and phenotype for each parent below. Sex Genotype Phenotype Male Female Step 1: Determine the different gamete combinations that each parent can contribute to the offspring. Sex Gamete 1 Gamete 2 Gamete 3 Gamete 4 Male Female Step 2: Fill in the Punnett Square below Male gametes place across ? Female Gametes: Place below: ? Step 3: Find the Phenotype of each of the 16 combinations in your Punnett Square page. Phenotype youve found in offspring Number of offspring with this phenotype Cross 3: Please write the number of the cross you are performing: ______________ Then fill in the genotype and phenotype for each parent below. Sex Genotype Phenotype Male Female Step 1: Determine the different gamete combinations that each parent can contribute to the offspring. Sex Gamete 1 Gamete 2 Gamete 3 Gamete 4 Male Female Step 2: Fill in the Punnett Square below Male gametes place across ? Female Gametes: Place below: ? Step 3: Find the Phenotype of each of the 16 combinations in your Punnett Square page. Phenotype youve found in offspring Number of offspring with this phenotype Questions: 1. Are gametes haploid or diploid? What about the offspring, are they haploid or diploid? (1pt) 2. a) Can two purple flowered and yellow seeded parents produce offspring that have white flowers and green seeds? Explain using a Punnett square why you think this outcome is possible or not. (1 pt) b) Can two short and green seeded parents produce offspring that are tall and have yellow seeds? Explain using a Punnett square why you think this outcome is possible or not. (1 pt)

Explanation / Answer

What is a gene?

Give an example of 2 alleles of a human gene. (0.5 pts)

Human blood groups are controlled by 3 alleles IA, IB and i

L and l alleles control the dark or light hair, LL or Ll or dark hari and ll for light hair

b) What is the difference between an organism that is a homozygote and one that is a heterozygote? (0.25 pts)

In homozygote, the trait is the result of two of the same alleles (E.g. LL alleles for hair color)

In heterozygote, the trait is the result of two different alleles (E.g. Ll alleles for hair color)

c) What is the difference between an organisms genotype and its phenotype? (0.25 pts)

Genotype is the alleles that the organism is carrying for a particular characteristic. E.g LL, Ll or ll

Phenotype is the outward appearance of that characteristic genotype

LL – Dark hair

Ll- Dark hair

ll-light hair (In all these 3 cases, the hair color is phenotype, which appears outside)

Flower color Purple (PP) and White (pp)

Plant Height Tall (TT) and Short (tt)

Seed Shape Smooth (SS) and Wrinkled (ss)

Seed Color Yellow (YY) and Green (yy)

Flower color

Homozygous dominant (PP)

Homozygous recessive(pp)

Heterozygous(Pp)

Plant Height

Homozygous dominant(TT)

Homozygous recessive(tt)

Heterozygous(Tt)

Seed Shape

Homozygous dominant(SS)

Homozygous recessive(ss)

Heterozygous(Ss)

Seed Color

Homozygous dominant(YY)

Homozygous recessive(yy)

Heterozygous(Yy)

Gametes for Flower color: Possible gametes

Homozygous dominant (PP) ------P

Homozygous recessive (pp) -------p

Heterozygous (Pp) ------------------P and p

Analysis of cross between four characters

81 Yellow, Round, Tall and Purple

27 Yellow, Round, dwarf and white

27 Yellow, dwarf, Tall and Purple

3 Yellow, wrinkled, dwarf and white

27 green, Round, Tall and Purple

3 green, Round, dwarf, white

9 Yellow, wrinkled, Tall and Purple

1 green, wrinkled, dwarf and white

: 1. Are gametes haploid or diploid? What about the offspring, are they haploid or diploid? (1pt) 2.

Gametes are haploid and offsprings are diploid

a) Can two purple flowered and yellow seeded parents produce offspring that have white flowers and green seeds?

If the parent is carrying heterozygous allele, then they can produce offspring with white flowers and green seeds.

Purple flower Pp

Green seeds yy

PY (purple flower, Yellow seeds)

pY(white flower, Yellow seeds)

Py (Purple flower, green seeds)

py (white flower, green seeds)

Explain using a Punnett square why you think this outcome is possible or not. (1 pt)

b) Can two short and green seeded parents produce offspring that are tall and have yellow seeds? Explain using a Punnett square why you think this outcome is possible or not. (1 pt)

No, it can’t produce, as dwarf is a recessive character, so it is tt. For tall plant we need T, so a tt alleles carrying plant can’t produce tall plant

tY (dwarf , Yellow seeds)

tY(dwarf, Yellow seeds)

tY (dwarf, green seeds)