3.4 IB Inheritance

The genotype of this flower is....

• homozygous recessive

• heterozygous

• homozygous dominant

• white

Answer explanation

homozygous = same alleles

recessive = lower case

Tags

NGSS.HS-LS3-1

NGSS.HS-LS3-2

To express a recessive trait you must be....

• homozygous dominant

• heterozygous

• heterozygous recessive

• homozygous recessive

Answer explanation

Remember, the presence of one dominant allele will mask or overpower any recessive allele present.

Tags

NGSS.HS-LS3-1

The physical appearance of a trait is called.....

• Genotype

• Phenotype

• Homozygous

• Heterozygous

Answer explanation

Remember, genotype is about the genes, phenotype is about the appearance (think of pheno for face).

Tags

NGSS.HS-LS3-1

Mendel's law of segregation states that during meiosis, the alleles that control each trait separate, and only _________________ from each pair is/are passed to the offspring

• one allele

• the dominant trait

• two alleles

• the recessive trait

Answer explanation

The whole point of meiosis is so that only one allele is present in each sex cell so that the resulting zygote obtains two alleles, one from each parent.

Tags

NGSS.HS-LS3-1

A roan cow shows co-dominance in fur color (red & white are both expressed). What is the phenotypic ratio expected if a roan cow and a roan steer mate together?

• 100% Roan

• 1:1 Red:White

• 1:1 Red:Roan

• 1:2:1 White:Roan:Red

• 1:1 White:Roan

Answer explanation

Tags

NGSS.HS-LS3-1

NGSS.HS-LS3-2

Ken is blood type B and Sally is blood type A. How can they have children who are types A, B, AB, and O?

• Ken: I^Bi

  Sally: I^Ai

• Ken: I^BI^B

  Sally I^Ai

• Ken: I^Bi

  Sally: I^AI^A

• Ken: I^BI^B

  Sally: I^AI^A

Answer explanation

Type O is recessive, so two recessive 'i' alleles must be present. Therefore both parents must be heterozygous and carry the recessive 'i' allele.

Tags

NGSS.HS-LS3-1

NGSS.HS-LS3-2

Orange or black fur is a single, X-linked co-dominant trait in cats. Calico cats have white fur with patches of orange and black. Is it true that calico cats can only be female?

• Yes, because they have 2 'X' chromosomes, and therefore can have both the orange and black alleles (X^OX^B)

• No, males can be calico because they can have both the alleles for orange and black (X^OY^B)

• Yes because the trait is found on the X chromosome (X^OBX)

• No, males can be calico because the trait is found on the X chromosome (X^OBY)

Answer explanation

Calico coloring is codominant and sex-linked. To have both colors you need both alleles, but as they are only found on X chromosomes and only females have two X chromosomes, calico cats can only be female.

Colorblindness is a recessive X-linked disorder.

Which genotype represents a male with normal vision?

• X^NY^N

• XⁿYⁿ

• X^NY

• XⁿY

Answer explanation

1. Men have XY

2. The allele is only on the X

3. If colorblindness is recessive then the X must have the recessive (lowercase) allele

Tags

NGSS.HS-LS3-1

Jim has type AB blood. His dad could be type O.

• 
• 
• 

Answer explanation

To be type O you must get a recessive allele from both parents. If the dad is AB that means his alleles are A and B - no recessive present.

Tags

NGSS.HS-LS3-1

NGSS.HS-LS3-2

Colorblindness is more common in males than in females because......

• fathers pass the allele for colorblindness to their sons only

• the allele for colorblindness is located on the Y chromosome

• the allele for colorblindness is recessive and located on the X chromosome

• males who are colorblind have two copies of the allele for colorblindness

Answer explanation

Males only get one X allele, so don't have the chance of having a second X with the dominant allele to negate the condition.

Tags

NGSS.HS-LS3-1

NGSS.HS-LS3-2