Punnet squares and genetic diagrams

Punnet squares and genetic diagrams

Revise the terms alleles, phenotype and genotype

Have a go at the questions on the next ten slides

Multiple Choice

1. Alternative forms of a gene are called

• Alleles

• Phenotype

• DNA

Multiple Choice

2. The physical appearance of an organism based on traits

• Genotype

• Phenotype

Multiple Choice

3. Being tall or short are examples of _______________

• Genotype

• Phenotype

Multiple Choice

4. Your particular combination of alleles is called your:

• genotype

• phenotype

Multiple Choice

5. Hair colour is an example of

• genotype

• phenotype

Multiple Choice

6. Having the genes for baldness is an example of

• genotype

• phenotype

Multiple Choice

8. Having blue eyes is an example of

• genotype

• phenotype

Multiple Choice

9. Having the genes for blue eyes is an example of

• genotype

• phenotype

Multiple Choice

10. Having genes that make you more likely to be good at sprinting is an aspect of

• genotype

• phenotype

Multiple Choice

7. An organism's _______ describes its genetic composition.

An organism's _______ describes its appearance or observable characteristics.

• phenotype; genotype

• genotype: phenotype

Extension question

In your book write a definition of an allele, genotoype and phenotype, and give examples.

You can go back to the slides to get ideas

How does genotype determine phenotype?

• To know the difference between dominant and recessive alleles

• To recognise homozygous dominant, homozygous recessive, and heterozygous genotypes

• To be able to follow a genetic diagram

• To determine the probability of a genotype using a punnett square

Genetic diagrams

• The genetic diagram shows the genotypes of two flowers for phenotype - petal colour

• Allelles for a particular gene are given a letter. The letter is either capital or lower case

• Look at the flowers what do you think R and r represent?

• What is the probability of the offspring having purple flowers?

Genetic diagrams -key terms

• Allele - e.g R or r

• Genotype - e.g RR, Rr or rr

• Homozygous - same

• Homozygous dominant - e.g. RR

• Homozygous recessive - e.g. rr

• Heterozygous - different - e.g Rr

• Now have a practice: (15 questions)

Multiple Choice

BB, Bb, and bb are examples of _________________

• Dominant

• Homozygous

• Genotype

• Phenotype

Multiple Choice

This type of allele masks the recessive allele and it's symbol is written as a capital letter:

• Dominant

• Homozygous

• Genotype

• Phenotype

Multiple Choice

This trait will always be expressed if present because it will mask the expression of others

• stem cells
• heterozygous
• dominant
• recessive

Multiple Choice

In rabbits, black fur (B) is dominant over brown fur (b). If a rabbit has brown fur, what can you conclude about its genotype?

• It is BB.
• It is Bb
• It is brown
• It is bb.

Multiple Choice

The genotype of:  bb   will have the PHENOTYPE of...

• black fur
• white fur
• course hair
• fine hair

Multiple Choice

The genotype of:  Bbll  will have the PHENOTYPE of...

• black fur/short tail
• black fur/long tail
• white fur/short tail
• white fur/long tail

Multiple Choice

If A = red fur and a = white fur, what color fur would Aa be?

• red

• white

• purple

• blue

Multiple Choice

The genotype of:  AA  will have the PHENOTYPE of...

• albinism
• normal pigment
• albino carrier

Multiple Choice

The genotype of:  albino carrier  will have the alleles of...

• Aa
• AA
• aa

Multiple Choice

The prefix "hetero" means

• different

• ugly

• fancy

• same

Multiple Choice

Which of the following represents alleles for the heterozygous genotype?

• Aa

• aa

• AA

Multiple Choice

The genotype of:  Heterozygous Course Hair  will have the alleles of...

• Hh
• HH
• hh

Multiple Choice

The prefix "homo" means

• different

• same

• tomorrow

• never

Multiple Choice

Which of the following represents alleles for the homozygous dominant genotype?

• Aa

• aa

• AA

Multiple Choice

Which of the following is homozygous recessive?

• rr

• AA

• TT

• Ff

Punnett squares

• We can represent all the possible genotypes in a punnett square

• The columns represent the alleles from one parent and rows the other parent

• Look at the diagram - which gender is homozygous? Is this recessive or dominant?

• What is the probability of the offspring being male?

• Now have a practice (5 questions)

• Homework - review your answers and make 2 flashcards for revision

Multiple Choice

What genotype would go in box 2? And is it Homozygous or Heterozygous?

• BB Heterozygous

• Bb Heterozygous

• bb Homozygous

• Bb Homozygous

Multiple Choice

What allele combination should go in the missing box?

• AA
• Aa
• aa
• none of these

Multiple Choice

What is the probability of heterozygous offspring?

• 25%
• 50%
• 0%
• 100%

Multiple Choice

If A = green pods and a = yellow pods, what are the GENOTYPIC RATIOS of the offspring in the Punnett square?

• 100% green pods

• 100% yellow pods

• 100% heterozygous

• 100% homozygous dominant

Multiple Choice

If A = red fur and a = white fur, what are the GENOTYPIC ratios of the offspring based on the Punnett Square?

• 25% heterozygous

• 50% purple

• 75% red fur and 25% white fur

• 25% homozygous recessive, 50% heterozygous, 25% homozygous dominant