Human Inheritance Review And Reinforce Answer Key - Fill and Sign ... - Free Printable

Let’s solve this step by step.

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Part A: Hemophilia (X-linked recessive)

We’re told:
- The father has hemophilia → his genotype is X^hY (since males have one X and one Y; if he has the disease, his X must carry the recessive allele).
- The mother is a carrier → her genotype is X^HX^h (she has one normal allele and one disease allele, but doesn’t show symptoms because it’s recessive).

Now let’s do the Punnett square for their children:

Mother’s gametes: X^H or X^h
Father’s gametes: X^h or Y

So possible offspring:

| | X^H (mom) | X^h (mom) |
|----------|----------------------|----------------------|
| X^h (dad) | X^HX^h → daughter, carrier | X^hX^h → daughter, has hemophilia |
| Y (dad) | X^HY → son, healthy | X^hY → son, has hemophilia |

So we get 4 possible outcomes, each equally likely (25% each):

1. Daughter, carrier (X^HX^h)
2. Daughter, affected (X^hX^h)
3. Son, healthy (X^HY)
4. Son, affected (X^hY)

→ So 50% of all children are likely to have hemophilia? Let’s check:

Affected children: #2 and #4 → that’s 2 out of 4 = 50%

But wait — question A asks: “What percentage of children are likely to have hemophilia?”

Yes — 2 out of 4 = 50%

BUT — hold on! In real biology, females need TWO copies to be affected. Here, the daughter with X^hX^h WOULD have hemophilia — yes, because it’s recessive, so two copies mean she expresses it.

So yes — 50% of children total will have hemophilia.

Wait — let me double-check:

Offspring:

- Girl 1: X^HX^h → carrier, not affected
- Girl 2: X^hX^h → affected
- Boy 1: X^HY → unaffected
- Boy 2: X^hY → affected

So affected: girl 2 and boy 2 → 2 out of 4 → 50%

✔ Correct.

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Part B: Colorblindness (also X-linked recessive)

Given:
- Mother is colorblind → genotype: X^cX^c (must have two recessive alleles to express it as female)
- Father is NOT colorblind → genotype: X^CY (normal vision)

Punnett Square:

Mother’s gametes: only X^c (both chromosomes same)
Father’s gametes: X^C or Y

Offspring:

| | X^c (mom) | X^c (mom) |
|----------|----------------------|----------------------|
| X^C (dad) | X^CX^c → daughter, carrier | X^CX^c → daughter, carrier |
| Y (dad) | X^cY → son, colorblind | X^cY → son, colorblind |

Actually, since mom gives only X^c, and dad gives either X^C or Y:

All daughters: get X^C from dad + X^c from mom → X^CX^c → carriers, NOT colorblind (because they have one dominant normal allele)

All sons: get Y from dad + X^c from mom → X^cY → colorblind (only one X, and it’s the bad one)

So:

→ All daughters: carriers, not colorblind → 0% of daughters are colorblind
→ All sons: colorblind → 100% of sons are colorblind

Total children: half sons, half daughters → so overall, 50% of children are colorblind (all the boys), but the questions ask specifically about daughters and sons.

Question III: What percentage of female children are likely to be colorblind?

→ Daughters are all X^CX^c → none are colorblind → 0%

Question IV: What percentage of male children are likely to be colorblind?

→ Sons are all X^cY → all are colorblind → 100%

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Building Vocabulary Section:

These are fill-in-the-blank definitions.

8. Alleles that are more than 2 genes that code for a single trait are called → polygenic traits
*(Example: skin color, height — controlled by multiple genes)*

9. _________ have alleles that are passed down from parent to child on sex chromosome. → Sex-linked traits

10. An ____________ is a person who carries a recessive allele but does not express it. → carrier

11. When a trait is determined by a single gene with two alleles, one dominant and one recessive, it is said to follow __________ inheritance. → Mendelian (or sometimes “simple” or “complete dominance”, but “Mendelian” is standard term here)

Wait — let’s read carefully:

“An ____________ is a person who carries a recessive allele but does not express it.” → That’s definitely carrier

“When a trait is determined by a single gene with two alleles...” → This describes classic Mendel pea plant stuff → Mendelian inheritance

But let’s confirm wording:

The sentence says: “When a trait is determined by a single gene with two alleles, one dominant and one recessive, it is said to follow __________ inheritance.”

Yes — Mendelian

Sometimes called “simple dominance”, but “Mendelian” is the correct scientific term.

Also, #8: “Alleles that are more than 2 genes that code for a single trait” — actually, the phrasing is awkward. It should say: “Traits that are controlled by more than 2 genes...” → those are polygenic traits

#9: “_________ have alleles that are passed down from parent to child on sex chromosome.” → These are sex-linked traits

#10: “An ____________ is a person who carries a recessive allele but does not express it.” → carrier

#11: As above → Mendelian

Wait — looking back at the worksheet layout:

It says:

8. Alleles that are more than 2 genes that code for a single trait are called _______________

That sentence is grammatically off — probably meant: “Traits that are controlled by more than two genes...”

Answer: polygenic traits

9. _______________ have alleles that are passed down from parent to child on sex chromosome.

Answer: Sex-linked traits

10. An _______________ is a person who carries a recessive allele but does not express it.

Answer: carrier

11. When a trait is determined by a single gene with two alleles, one dominant and one recessive, it is said to follow _______________ inheritance.

Answer: Mendelian

Some might say “complete dominance”, but “Mendelian” is broader and fits better here.

Actually, in many textbooks, this exact phrase uses “Mendelian”.

Let me verify logic again for genetics parts.

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Double-check Part A:

Father: X^hY
Mother: X^HX^h

Children:

Daughters:
- Get X^h from dad → always
- Get either X^H or X^h from mom → so 50% X^HX^h (carrier), 50% X^hX^h (affected)

Sons:
- Get Y from dad
- Get either X^H or X^h from mom → 50% X^HY (healthy), 50% X^hY (affected)

So among ALL children:

- 25%: carrier daughter
- 25%: affected daughter
- 25%: healthy son
- 25%: affected son

→ Affected children: affected daughter + affected son = 50%

Question I: What percentage of children are likely to have hemophilia? → 50%

Question II: Is either the mother or father likely to be colorblind? → Wait, no — this is under hemophilia section? Actually, looking back:

In the image, after Part A (hemophilia), there's:

I. What percentage of children are likely to have hemophilia? → 50%

II. Is either the mother or father likely to be colorblind? → Hmm, this seems misplaced. But in context, it’s still under hemophilia? No — probably typo or mislabeling.

Wait — looking at original structure:

After the hemophilia cross, it says:

I. What percentage of children are likely to have hemophilia?

II. Is either the mother or father likely to be colorblind? ← This doesn't make sense here. Probably it's a mistake — maybe it should be "Is either parent affected?" or something.

But in the problem, for hemophilia:

Father HAS hemophilia → so he is affected.

Mother is carrier → not affected.

So answer to II: Yes, the father is likely to have hemophilia (he does).

But the question says “colorblind” — that must be an error. Because we haven’t introduced colorblindness yet.

Looking at the worksheet layout:

Actually, in the user’s image description, after Part A (hemophilia), it lists:

I. % children with hemophilia
II. Is either parent likely to be colorblind? ← This is probably a typo — should be “hemophilia”

Because colorblindness is in Part B.

Perhaps it’s a copy-paste error in the worksheet.

But based on what’s written: “Is either the mother or father likely to be colorblind?” — in the context of hemophilia cross, neither is colorblind — we don’t know, but the question is irrelevant.

Wait — perhaps it’s asking within the hemophilia scenario whether either parent has colorblindness? But that’s not given.

This is confusing.

Alternative interpretation: Maybe “II” is part of the hemophilia section, and it’s a trick question — since colorblindness is different, and we’re not told anything about it, the answer is “no” or “not applicable”.

But that seems odd.

Perhaps it’s a labeling error, and “II” should be about hemophilia status of parents.

Let me re-read the original text provided:

From user input:

“A. Hemophilia ... [cross] ... I. What percentage of children are likely to have hemophilia? II. Is either the mother or father likely to be colorblind?”

That must be a mistake. Probably, “II” should be “Is either parent affected by hemophilia?” or similar.

Given that, and since father HAS hemophilia, answer is yes.

But it says “colorblind” — which is unrelated.

To resolve: Since the worksheet likely has a typo, and given the context, I think “II” is meant to ask if either parent has the disorder being discussed (hemophilia). Father does.

But strictly speaking, as written: “Is either the mother or father likely to be colorblind?” — we have no information about colorblindness in this family, so answer is “No” or “Not enough information”.

But that seems unfair.

Another possibility: In some worksheets, they mix questions, but here it’s clearly separated into A and B.

Looking ahead, Part B is colorblindness, so probably “II” is misplaced.

I think safest is to assume it’s a typo and answer based on hemophilia: father is affected, so yes.

But let’s see the exact wording in the user’s message:

“I. What percentage of children are likely to have hemophilia?
II. Is either the mother or father likely to be colorblind?”

Since colorblindness is not mentioned in Part A, and we’re only talking about hemophilia, the answer should be: We don’t know, or no — but that’s not satisfactory.

Perhaps “colorblind” is a red herring, and we should ignore it? Unlikely.

Wait — another idea: Maybe “II” is referring to the fact that both disorders are X-linked, and perhaps implying if the father having hemophilia means he might also be colorblind? But no, they are different genes.

I think the best approach is to note that in the hemophilia cross, the father has hemophilia, so he is affected by that disorder, but regarding colorblindness, there’s no data, so probably the intended question was about hemophilia.

Given that, and to match common worksheet patterns, I’ll assume “II” meant “is either parent affected by hemophilia?” → father is, so yes.

But to be precise, as written, for colorblindness: no information, so answer is “No” or “Cannot be determined”.

However, in educational contexts, when such errors occur, we go with intent.

Let me check online or standard problems.

Upon second thought, in many textbooks, after a cross, they ask about parental phenotypes.

For hemophilia:

- Father: affected (has it)
- Mother: carrier (not affected)

So if the question is “is either parent likely to have hemophilia?” → yes, father.

If it’s “colorblind”, then no.

But since the next part is colorblindness, perhaps “II” is accidentally placed.

I think for accuracy, I'll answer as written.

So for II: Is either the mother or father likely to be colorblind? — Based on given info, no. The father has hemophilia, not necessarily colorblindness. Mother is carrier for hemophilia, no mention of colorblindness. So answer: No

Similarly, for Part B, we have specific info.

So let's finalize:

Part A:

I. 50%
II. No (since no info suggests they are colorblind; father has hemophilia, which is different)

Part B:

III. 0% (daughters are all carriers, not colorblind)
IV. 100% (sons are all colorblind)

Vocabulary:

8. polygenic traits
9. Sex-linked traits
10. carrier
11. Mendelian

Now, write final answers.

Final Answer:

A. I. 50%
II. No

B. III. 0%
IV. 100%

Building Vocabulary:
8. polygenic traits
9. Sex-linked traits
10. carrier
11. Mendelian