Genetics

Question 1

The structure of DNA

Answer 1

Structure: DNA forms a double helix.
- When the 2 complementary strands of DNA come together they will twist naturally into a helix
- This double-stranded helix is considered a single DNA molecule.

Question 2

6. General definition of mutations

Answer 2

• When chromosomes are not rearranged properly
• Block mutations: Rearrangement of whole segments of chromosomes

Question 3

Incomplete dominance vs codominance

Answer 3

• Incomplete = both alleles are expressed and the phenotype is a “blend”
• Codominance = both alleles are expressed and the phenotype is a mixture or patches of both of them (Like on a cow both colours white and brown would appear together spotted)
• Incomplete dominance is when it is blended and codominance is when it appears together.

Question 4

what is Nondisjunction?

Answer 4

• Failure of chromosomes to separate properly
• Anaphase I: Failure of tetrad to separate, During independent assortment
• Anaphase II: Failure of dyads to separate

Question 5

. Each of the block mutations
(Duplication)

Answer 5

Duplication: A segment of the chromosome is copied
The copy and the original both exist in the genome
The duplicated copy can be on the original copy or on
another chromosome Effect: May lead to gene dosage
effects or functional changes due to the presence of
additional genetic material.

Question 6

. Each of the block mutations
(Inversion)

Answer 6

Inversion: Reversal of the orientation of a segment of DNA
within the chromosome.Effect: Alters the gene order,
potentially disrupting gene regulation or function.

Question 7

. Each of the block mutations
(Insertion)

Answer 7

Insertion: Addition of extra DNA sequences into the genome.Effect: Alters the reading frame of the gene, potentially leading to functional changes.

Question 8

. Each of the block mutations
(Translocation)

Answer 8

Translocation: Movement of a segment of DNA from one chromosome to another.Effect: This can result in the fusion of genes from different chromosomes, leading to altered gene expression.

Question 9

. Each of the block mutations
(Deletion)

Answer 9

Deletion: Loss of a segment of chromosome
This may occur due to 2 breaks in the chromosome releasing a
segment while the 2 free ends rejoin to form a shortened
chromosome Effect: Loss of genetic material can lead to
the absence or alteration of gene function.

Question 10

what is karyotypes?

Answer 10

A picture of an individual complete set of chromosomes, organized in a systematic way, ( a human karyotype usually has 4 rows)

Question 11

3 characteristics to identify a chromosome

Answer 11

• chromosome size
• the position of the centromere
• banding pattern

Question 12

Application of karyotypes

Answer 12

• Identifying sex
• Identifying chromosomal abnormalities like if there are extra, wrong, or missing.

Question 13

. Each of the block mutations with examples of the disorders (deletion)

Answer 13

Deletion Example: Cri-du-chat disorder (french for cry of
the cat. Infants have a high-pitched cry that sounds like a
cat, delayed development, small head size (microcephaly),
weak muscle time in infancy, and Distinctive facial features:
widely set eyes, low set ears, small jaw, and rounded face.

Question 14

Where does DNA synthesis occur?

Answer 14

DNA is held in the nucleus. Therefore, Synthesis occurs in the nucleus of the cell.

Question 15

Each of the block mutations with examples of the disorders (duplication)

Answer 15

Duplication Example: Fragile X syndrome. Most common
identifiable form of inherited intellectual disability.
Prevalence: males 1 in 4000, Female 1 in 8000. Physical
Features: relatively large head, long face with prominent
Ears, largish jaw and double jointedness.

Question 16

Autosomal dominant vs autosomal recessive

Answer 16

Autosomal dominant traits pass from one parent onto their child. Autosomal recessive traits pass from both parents onto their child.

Question 17

Each of the block mutations with examples of the disorders (inversion)

Answer 17

Inversion Example: Hemophilia is a disease that inhibits the
ability of blood to clot. An inversion of an intron on the F8
gene disrupts a coagulation factor and allows excessive
bleeding because of a lack of proper clotting.

Question 18

Each of the block mutations with examples of the disorders (insertion)

Answer 18

Insertion Example: Cystic fibrosis is a lung disease caused
by a frameshift mutation that alters the CFTR (cystic fibrosis transmembrane conductance regulator) gene.

Question 19

Each of the block mutations with examples of the disorders (translocation)

Answer 19

Translocation Example: Down Syndrome is an abnormal cell
division involving chromosome 21 occurrence. These cell division abnormalities result in an extra partial or full chromosome 21. This extra genetic material is responsible for the characteristic features of a broad flat face, slanting eyes, short, growth failure, mental disabilities, congenital heart disease, and simian crease) and developmental problems of Down syndrome.

Question 20

General definition of mutations

Answer 20

-When chromosomes are not rearranged properly
-Block mutations – Rearrangement of whole segments of chromosomes

Question 21

Nondisjunction

Answer 21

• Failure of chromosomes to separate properly
  Anaphase I
• Failure of tetrad to separate
  During independent assortment
  Anaphase II
• Failure of dyads to separate

Question 22

Sex-linked disorders

Answer 22

X-Linked Inheritance Pattern:
- X-linked recessive disorders are more likely to express itself in males than females
- Males need only one copy of the recessive allele for expression since they only have one copy of the X chromosome
- Females need two copies of the recessive allele for expression
- Heterozygous females will not be affected by an X-linked recessive disorder
X-Linked Disorders:
- Hemophilia
- Duchenne Muscular Dystrophy
- Color Blindness
- Baldness

Question 23

x-linked recessive vs dominant

Answer 23

Families with an X-linked recessive disorder often have affected males, but rarely affected females, in each generation. For X-linked dominant diseases, however, a mutation in one copy of an X-linked gene will result in disease for both males and females.

Question 24

explain how polygenic traits differ from traits controlled by a single gene

Answer 24

Polygenic traits are characteristics that are determined by the combined effects of multiple genes, often referred to as polygenes. Each gene may contribute a small additive effect to the overall phenotype.
Genetic Basis: Multiple genes, located at different loci on different chromosomes, contribute to the expression of the trait. Each gene may have multiple alleles.
(Monogenic Traits) Traits controlled by a single gene are determined by the interaction of alleles at a single gene locus. The gene may have different alleles that result in distinct phenotypes.
Genetic Basis: The trait is controlled by one gene, and the expression of the trait follows Mendelian inheritance patterns (e.g., dominant/recessive).

Question 25

explain why an understanding of meiosis helps explain inheritance patterns. Be sure to use the following terms in your explanation: independent assortment, crossing over, haploids and segregation of alleles.

Answer 25

Meiosis is an important process in understanding inheritance patterns because it makes genetic variation through independent assortment, crossing over, haploids, and allele segregation. During meiosis, homologous chromosomes split into gametes at random, resulting in independent assortment and an increase in the number of allele combinations. Crossing over during prophase I causes the exchange of genetic material across chromosomes, which contributes to genetic variation. Meiosis creates haploid gametes, each with a distinct set of alleles, and when these haploid gametes combine during fertilization, the resulting zygote gets one allele from each parent. Allele segregation ensures that offspring show specific traits based on the genetic information inherited from both parents.

Question 26

discuss why polygenic traits often result in a continuous range of phenotypes rather than distinct categories.

Answer 26

Polygenic traits are more than one gene that controls the expression of the same physical characteristic. Each gene involved in the trait may have multiple alleles, and the combination of these alleles leads to a wide spectrum of possible phenotypes. As more genes contribute to the trait, the range of possible phenotypes becomes increasingly diverse.

Question 27

Examples of polygenic traits with descriptions

Answer 27

Discrete or discontinuous traits:
- Traits occur in distinct categories
- Trait is there or not
- Ex. Mendelian inheritance, single genes, complete dominance
Continuous traits:
- The distribution of phenotypes in the population varies along a continuum
- Individuals differ by small degrees
- Ex. Height, blood pressure, reaction time, learning ability