Human genetics

Question 1

Who is known as the first geneticist?

Answer 1

Gregor Mendel.

Question 2

What organism did Mendel use in his experiments?

Answer 2

Garden peas.

Question 3

What is a mutation?

Answer 3

A permanent change in a gene.

Question 4

What is an allele?

Answer 4

An alternative form of a gene.

Question 5

Define homozygous.

Answer 5

Two identical alleles for a gene.

Question 6

Define heterozygous.

Answer 6

Two different alleles for a gene.

Question 7

What is a genotype?

Answer 7

The alleles an individual carries.

Question 8

What is a phenotype?

Answer 8

The observable traits of an individual.

Question 9

What does true-breeding mean?

Answer 9

The phenotype is always passed to offspring.

Question 10

What is the difference between haploid and diploid cells?

Answer 10

Haploid has one set of chromosomes; diploid has two.

Question 11

What are human gametes?

Answer 11

Egg and sperm.

Question 12

What is a zygote?

Answer 12

The diploid cell formed from fusion of gametes.

Question 13

What are the three Mendelian laws of inheritance?

Answer 13

Law of dominance, law of segregation, law of independent assortment.

Question 14

What is the law of dominance?

Answer 14

In a hybrid, only one trait (dominant) appears.

Question 15

What is the law of segregation?

Answer 15

Alleles separate so each gamete gets one.

Question 16

What is the law of independent assortment?

Answer 16

Alleles of different genes segregate independently.

Question 17

What genotype do F1 hybrids have?

Answer 17

Heterozygous (Pp).

Question 18

What phenotype do F1 hybrids express?

Answer 18

Dominant phenotype (e.g. purple flowers).

Question 19

What is the phenotypic ratio in the F2 generation from a hybrid cross?

Answer 19

75% dominant, 25% recessive.

Question 20

What is the genotypic ratio in the F2 generation from a hybrid cross?

Answer 20

1/4 homozygous dominant, 2/4 heterozygous, 1/4 homozygous recessive.

Question 21

What is meant by dominant and recessive phenotypes?

Answer 21

Dominant is expressed in heterozygotes, recessive is masked.

Question 22

Can all traits be explained by simple Mendelian dominance?

Answer 22

No, some traits show incomplete or codominance.

Question 23

What does independent assortment apply to?

Answer 23

Genes on different chromosomes.

Question 24

What causes dependent assortment?

Answer 24

Genes located close on the same chromosome.

Question 25

What is recombination?

Answer 25

Exchange of DNA segments during meiosis.

Question 26

What is a monogenic disease?

Answer 26

A disease caused by mutation in a single gene.

Question 27

What inheritance pattern does Huntington's disease follow?

Answer 27

Autosomal dominant.

Question 28

What is the inheritance pattern of cystic fibrosis?

Answer 28

Autosomal recessive.

Question 29

How is haemophilia inherited?

Answer 29

X-linked recessive.

Question 30

What pattern is seen in X-linked recessive diseases?

Answer 30

More males than females are affected.

Question 31

How can a pedigree help determine inheritance patterns?

Answer 31

It shows if a trait is dominant, recessive, or X-linked.

Question 32

What is genetic heterogeneity?

Answer 32

Different mutations in different genes cause the same disease.

Question 33

What is the difference between polygenic and monogenic diseases?

Answer 33

Monogenic: one gene; polygenic: multiple genes.

Question 34

What is the effect of the environment in genetics?

Answer 34

It can influence gene expression and phenotype.

Question 35

What does the law of segregation state about gametes?

Answer 35

Each gamete receives only one allele of a gene.

Question 36

What happens to chromosomes during random assortment?

Answer 36

They are randomly distributed during meiosis.

Question 37

What happens if recombination occurs between genes A and D?

Answer 37

Genes A and D segregate independently.

Question 38

What happens if recombination does not occur between two genes?

Answer 38

They are inherited together, leading to linkage.

Question 39

Which allele combinations result in a recessive phenotype?

Answer 39

Homozygous recessive (pp).

Question 40

Which combinations result in a dominant phenotype?

Answer 40

Homozygous dominant (PP) or heterozygous (Pp).

Question 41

How do you determine if a trait is dominant using a family pedigree?

Answer 41

If at least one parent is affected, trait is dominant.

Question 42

What is the most likely pattern if unaffected parents have an affected daughter?

Answer 42

Recessive pattern — both parents are carriers.

Question 43

What is the most likely pattern if parents and son are affected, but daughter is not?

Answer 43

Dominant pattern — affected parents, unaffected daughter.

Question 44

Which parent must carry the X-linked mutation for a son to be affected?

Answer 44

The mother must be at least a carrier.

Question 45

What is ploidy of human gametes?

Answer 45

Haploid.

Question 46

How does inheritance differ between autosomal dominant and recessive diseases?

Answer 46

Dominant: one parent affected; Recessive: both parents carriers.

Question 47

What does Mendel's law of segregation say about alleles?

Answer 47

Each gamete receives only one of the alleles.

Question 48

What kind of traits violate the law of independent assortment?

Answer 48

Linked genes on the same chromosome without recombination.

Question 49

Why is Mendelian genetics important in medicine?

Answer 49

It helps predict and diagnose inherited diseases.