5.4 Inheritance part 2 2HVTTO

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• Biologie
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• Leerjaar 2

5.4 Inheritance (part 2)

• Take off your jacket

• Put your things on your desk

       Book, notebook, pencil case

Bag on the floor

• Read pages 132-133

5

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00

second

+30 s

Lessongoals

• Understand: I can explain that genes can exist in different forms called alleles, and describe the difference between dominant and recessive alleles.

• Analyse: I can explain how alleles affect the phenotype in both homozygous and heterozygous combinations by using correct examples.

• Apply: I can use gene symbols to write down genotypes and fill in simple Punnett squares to predict the offspring's genetic combinations.

What is the best description of genes and alleles?

A

A gene is in the DNA An allele is on a chromosome

B

a gene is a characteristic an allele is a variant of this characteristic

C

allele and gene are synonymous

D

an allele is a characteristic a gene is a variant of this characteristic

Give an example of a gene

Healthy organisms always have 2 alleles of each gene. Explain why these alleles aren't always the same.

Homo- & heterozygous

Homo = same            hetero = different

Homozygous > alleles for the characteristic are the same 

Heterozygous > alleles of the characteristic are different

A man and woman have a baby. The man is homozygous for blond hair. The woman is homozygous for brown hair. Explain, will the baby be homozygous or heterozygous for hair colour?

Dominant and recessive

• Alleles are either dominant or recessive

• Dominant is 'stronger' than recessive

• A dominant trait means dominant for all members of the species

• Heterozygous genotype > Dominant allele visible in phenotype

Example:

If blond is dominant over brown hair, it means that for every human blond is dominant!

It doesn't differ per human (or animal/plant/etc.) if a certain allele is dominant or recessive!

There are 3  possibilities:

Heterozygous = 1 recessive allele and 1 dominant allele > dominant phenotype

Homozygous dominant = 2x dominant allele > dominant phenotype

Homozygous recessive = 2x recessive allele > recessive phenotype

Cats can have black or red fur colour. Black is dominant. What are possible genotypes for a black cat?

A

Always homozygous

B

Always heterozygous

C

Homozygous or heterozygous

D

Cats can have black or red fur colour. Black is dominant. What are possible genotypes for a red cat?

A

Always homozygous

B

Always heterozygous

C

Homozygous or heterozygous

D

Flowers of the bean plant can be pink or white. Plant 1 has white flowers and is heterozygous. Plant 2 has pink flowers and is homozygous. Which colour is recessive?

A

White

B

Pink

C

Impossible to know

Gene symbols

Alleles are usually shown using a letter.

• Alleles of the same gene use the same letter

• Dominant = capital letter,  Recessive = normal letter

• AA = homozygous dominant

• aa = homozygous recessive

• Aa = heterozygous

Often the letter A is used. But other letters are also possible.

If the choice is yours, be sure to use a letter where capital and small are clearly different! like:

Bb

Gg

Rr

Sometimes people write aA instead of Aa.

Always put the capital letter first! in a homozygous genepair.

(it shows that dominant is the strongest)

Flowers of the beanplant can be pink or white. Plant 1 has white flowers and is heterozygous. Use gene symbols to show the genotype of this flower. Use the first letter of the dominant allele

For humans, dark hair is dominant over blond hair. A man is heterozygous for hair colour. What is his geno- and phenotype?

A

AA and dark hair

B

aa and blond hair

C

Aa and dark hair

D

Aa and blond hair

A father has genotype AA, the mother Aa. Which genotypes are possible for their kids?

A

AA, aa en Aa

B

Aa en aa

C

Aa en AA

D

aa en AA

Alleles in body cells and sperm cells (sex cells) of the father

Alleles in body cells and egg cells (sex cells) of the mother 

Possible allele pairs in fertilized egg cells and body cells of the offspring of these parents

Mix the alleles

Try making lots of different correct combinations

A

A

A

A

A

A

A

A

A

A

A

A

A

A

A

A

A

A

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

a

What you should do: 5.4

• TB: pages 132-133

• WB: asgmt  16-22 pgs. 163-165

• Lt: asgmt 1-6

Done with the above?

• Work on the next chapter(s)

• Learn for the test 

• Make other homework

• Read a book

Zs = Working in Silence

• No asking questions

• Silent, don't disturb anyone

• Stay at your  desk

6

minute

00

second

+30 s

What you should do: 5.8

• Read pages 164-166

• Do asgmt 1-3 pgs. 163-165

• Challenge: how it fits together pgs. 158-159 

Done with the above?

• Work on the next chapter(s)

• Learn for the test 

• Make other homework

• Read a book

Zw = Working with whispering

• Teacher is available for questions

• Only whisper with the student next to you

• Stay at your  desk

2 Parents both have blue eyes. They have a son with green eyes. What is (probably) the genotype of the parents and son? Use gene symbols

Tidy Duty

3 people each lesson

• Desks: empty and straight

• Chairs:  underneath the desks OR end of day: on the desks

• Floor: no rubbish