Midterms

Question 1

When did Gregor Mendel start experimenting, and what did he experiment with?

Answer 1

In 1866, Pea plants about inheritance

Question 2

What is his work that allows him to see the inheritance

Answer 2

His work with self-fertilization and cross—
Pollination allowed him to discover patterns in inheritance.

Question 3

In his experiment, how long did it take to do it? And what is it called?

Answer 3

From 1857–1863, Mendel conducted
hybridization experiments with 24,034 pea
plants.

Question 4

What is genes called before?

Answer 4

“distinct units”

Question 5

offspring with
different gene variants
from each parent.

Answer 5

Hybrids

Question 6

plants that always produce
offspring with the same
trait.

Answer 6

True-breeding

Question 7

cross involving one trait with two forms.

Answer 7

Monohybrid Cross

Question 8

a physical
characteristic that is
inherited from one
generation to the next.

Answer 8

Trait

Question 9

Another word for factors

Answer 9

Genes

Question 10

difference forms of a gene

Answer 10

Allele

Question 11

TRUE OR FALSE:Two factors (alleles) control each specific characteristic (gene). These factors (alleles) are separated during the formation of gametes (sex cells).

Answer 11

TRUE

Question 12

In a genetic experiment, two individuals that are homozygous for different alleles of a single gene are crossed. The gene controlling the trait has multiple allelic variations. What type of genetic cross is being performed, and what can this cross help determine about the offspring?

Answer 12

This type of genetic cross is called a monohybrid cross involving multiple alleles.

Since the parent (P) generation organisms are homozygous for different alleles of the same gene, this cross helps to:

Identify the genotype and phenotype ratios of the offspring,

Determine how the alleles interact (dominant, recessive, co-dominant, etc.),

And study inheritance patterns of a single gene with multiple allelic forms.

For example, if one parent is AA and the other is aa, all F₁ offspring will be Aa, and observing their traits can reveal which allele is dominant or recessive. If more than two alleles exist in the population (e.g., A, a, Aʹ), the experiment can also help determine how those multiple alleles influence the trait.

Question 13

What is elementen

Answer 13

Genes

Question 14

are pieces of DNA that code for proteins that affect physiology and contribute to specific traits or functions.

Answer 14

Genes

Question 15

What are the gene variants that differ based on the specific nucleotide base at a particular genomic location called, and how do they contribute to an individual’s genotype?

Answer 15

Alleles

Question 16

What is the Law of Segregation in
Mendelian genetics?

Answer 16

Each gamete produced by an organism has a single gene copy that is chosen at random. This is referred to as the segregation law.

Question 17

is a genetic cross between two individuals that are heterozygous for two different traits. It is used to study how two genes (each with two alleles) are inherited together.

Key Points:
It involves two traits (e.g., seed shape and seed color in peas).

The parents in a typical dihybrid cross are both heterozygous for both traits (e.g., AaBb × AaBb).

Each gene follows Mendelian inheritance (dominant and recessive patterns).

It can show whether the genes are inherited independently (Mendel’s Law of Independent Assortment).

Example:
If A = round seeds, a = wrinkled seeds,
and B = yellow seeds, b = green seeds,
a dihybrid cross of AaBb × AaBb would result in a 9:3:3:1 phenotypic ratio:

9 round yellow

3 round green

3 wrinkled yellow

1 wrinkled green

Answer 17

Dihybrid crosses

Question 18

Formula:

Answer 18

2n (n- # of heterozygotes

Question 19

describe how single-gene
traits are passed from one generation to the next. They help predict the likelihood of an individual inheriting a trait.

Answer 19

Modes of inheritance

Question 20

TRUE OR FALSE: Relatives (like first cousins) are more
likely to carry the same rare allele.

Answer 20

TRUIE

Question 21

“Individuals with shared ancestry are more likely to carry the same recessive alleles, which increases the risk of recessive genetic disorders in their offspring

Answer 21

Consanguinity

Question 22

In severe diseases like ______, the affected
Children rarely survive.

Answer 22

Tay-Sachs

Question 23

TRUE OR FALSE: If one sibling is a known carrier, each adult sibling has a 2/3 chance of being a carrier—not 1/2—because a third option (being affected) is excluded by survival.

Answer 23

TRUE

Question 24

What are the key differences between recessive and dominant genetic disorders in terms of severity, age of onset, and how their alleles persist in the population?

Answer 24

Recessive disorders are often more severe and usually appear early in life, with carriers passing on the alleles without symptoms, which allows these alleles to persist in the population. Dominant disorders, on the other hand, may become rare if symptoms are severe and appear early because affected individuals might not reproduce; however, if symptoms appear later in life, such as in Huntington’s disease, the allele can remain in the population.

Question 25

What does a pedigree chart show and what information does it typically include?

Answer 25

A pedigree chart shows family relationships and maps which relatives have certain traits or disorders. It often includes genetic information such as genotypes, test results, or haplotypes.

Question 26

Pedigrees are not the same as:

Answer 26

A family tree (used in genealogy) A genogram (used in social work)

Question 27

Shapes:

Answer 27

Square = Male Circle = Female Diamond = Unspecified sex

Question 28

Lines:

Answer 28

Vertical lines = Generational connections (parent → child) Horizontal line between two shapes = Mating/partners Horizontal lines connecting siblings = Children of same parents

Question 29

Numbering:

Answer 29

Roman numerals (I, II, III...) = Generations Arabic numerals or names = Individuals within generations

Question 30

Shading

Answer 30

Fully shaded = Individual expresses the trait Half-shaded = Known carrier of the trait

Question 31

What is the genotype of an individual who lacks the enzyme to produce melanin, resulting in very pale skin and hair?

Answer 31

Homozygous Recessive (aa)

Question 32

are heterozygous and do not show symptoms but can pass on the gene.

Answer 32

Carriers (Aa)

Question 33

To produce an affected offspring, both parents must be ________

Answer 33

carriers or affected (aa or Aa).

Question 34

What is the process called that identifies individuals who have half the normal level of a key biochemical, such as the melanin enzyme, indicating they carry a genetic disorder?

Answer 34

Carrier Detection

Question 35

What is an Inconclusive Pedigree?

Answer 35

A pedigree that shows traits that could be explained by either autosomal dominant or autosomal recessive inheritance.

Question 36

Many traits are controlled by more than one gene

Answer 36

polygenic traits

Question 37

is a type of inheritance where neither allele is completely dominant over the other. Instead of one trait being fully expressed, the two alleles blend together, resulting in a third, intermediate phenotype.

Answer 37

Incomplete Dominance

Question 38

What dominance is If a red flower (RR) is crossed with a white flower (WW), and the offspring are all pink (RW), this is incomplete dominance. The pink color is a blend of red and white.

Answer 38

Incomplete Dominance

Question 39

is a type of inheritance where both alleles are fully and equally expressed in a heterozygous individual. Unlike incomplete dominance (where traits blend), codominance results in both traits appearing side by side without blending.

Answer 39

Codominance

Question 40

refers to patterns of inheritance that do not follow the basic laws proposed by Gregor Mendel, such as the Law of Segregation and the Law of Independent Assortment.

Answer 40

Non-Mendelian genetics

Question 41

The heterozygous phenotype is a blend of the two alleles. Example: Red (RR) × White (WW) = Pink (RW) flowers.

Answer 41

Incomplete Dominance

Question 42

Both alleles are fully expressed in the heterozygous form. Example: AB blood type or a black and white spotted animal.

Answer 42

Codominance

Question 43

More than two possible alleles exist in the population, but each person still gets only two. Example: Blood type has A, B, and O alleles.

Answer 43

Multiple Alleles

Question 44

Multiple genes influence a single trait. Example: Skin color, height, and eye color result from the interaction of several genes.

Answer 44

Polygenic Inheritance

Question 45

Genes located on the sex chromosomes (usually X). Example: Colorblindness and hemophilia are more common in males because they have only one X chromosome.

Answer 45

Sex-Linked Traits

Question 46

Genes inherited only from the mother, since mitochondria come from the egg cell. Affects things like cellular energy production.

Answer 46

Mitochondrial Inheritance

Question 47

One gene can mask or interfere with the expression of another. Example: A gene for albinism can mask other pigment genes.

Answer 47

Epistasis

Question 48

The hybrid (heterozygous) offspring displays a THIRD Phenotype!! Neither trait is completely dominant, as a result, there appears to be a blending phenotype.

Answer 48

Incomplete Inheritance

Question 49

occurs when one gene masks or modifies the effect of another gene at a different locus.

Answer 49

Epiptasis

Question 50

two recessive alleles at one gene mask the effect of another gene (like the albino example above).

Answer 50

Recessive Epistasis

Question 51

one dominant allele at one gene masks the expression of another gene.

Answer 51

Dominant Epistasis

Question 52

either of two genes can perform the same function; only one needs to be active for the trait to show.

Answer 52

Duplicate Gene Epistasis

Question 53

is a form of gene interaction in which one pair alleles (gene) masks phenotypic expression of another. It is also a form of polygenics.

Answer 53

Epistasis

Question 54

What is the difference between dominance and epistasis in terms of gene interaction and how traits are expressed?

Answer 54

Dominance involves intra-allelic interaction, meaning it occurs between alleles of the same gene. In this case, one allele hides or masks the effect of the other allele in the same gene pair (e.g., dominant vs. recessive alleles). Epistasis, on the other hand, involves inter-allelic interaction, which means it occurs between different genes at different loci. One gene can hide or alter the expression of a completely different gene, even if that second gene has its own dominant or recessive alleles.

Question 55

What is the difference between epistatic and hypostatic alleles in gene interaction?

Answer 55

Epistatic alleles are the ones that interfere with or mask the expression of another gene. Hypostatic alleles are the ones whose expression is being masked or interfered with by the epistatic gene. In epistasis, the epistatic gene controls whether or how the hypostatic gene is expressed.

Question 56

refers to the proportion of individuals with a specific genotype who actuallyu show the expected phenotype.

Answer 56

Penetrance

Question 57

100% of individuals with the gene express the trait.

Answer 57

Complete Penetrance

Question 58

Some individuals with the gene do not show the trait.

Answer 58

Incomplete (or Reduced) Penetrance

Question 59

refers to the degree or variation in which a trait is expressed in individuals with the same genotype.

Answer 59

Expressivity

Question 60

When a single pair of gene control the production of many characters, then it is called ______

Answer 60

pleiotropism. The gene is called pleiotropic gene.

Question 61

What genetic condition is caused by a mutation in the FBN1 gene, leading to long limbs, vision issues, and heart problems—an example of pleiotropy where one gene affects multiple body systems?

Answer 61

Marfan Syndrome

Question 62

What genetic condition is caused by a mutation in a single gene affecting red blood cells, leading to sickle-shaped cells, pain, organ damage, and also offers protection against malaria—an example of pleiotropy?

Answer 62

Sickle Cell Disease

Question 63

What is the term used when different genes can cause the same disease or trait?

Answer 63

Genetic heterogeneity

Question 64

How can deafness illustrate the concept of genetic heterogeneity?

Answer 64

Deafness can be caused by mutations in different genes, such as GJB2, MYO7A, and TMC1, all leading to hearing loss through different genetic pathways.

Question 65

Name one gene mutation that can cause deafness due to genetic heterogeneity.

Answer 65

GJB2 gene mutation

Question 66

Why is it important to understand genetic heterogeneity when diagnosing genetic disorders like deafness?

Answer 66

Because the same condition (like hearing loss) can result from different gene mutations, accurate diagnosis and treatment may depend on identifying the specific gene involved.

Question 67

What is the difference between allelic heterogeneity and locus heterogeneity?

Answer 67

Allelic heterogeneity occurs when different mutations in the same gene cause the same disease (e.g., various mutations in the CFTR gene causing cystic fibrosis). Locus heterogeneity occurs when mutations in different genes cause the same disease (e.g., retinitis pigmentosa caused by mutations in over 60 different genes).

Question 68

If multiple mutations in the CFTR gene all lead to cystic fibrosis, what type of genetic variation is this?

Answer 68

Allelic heterogeneity

Question 69

If a disease like retinitis pigmentosa can be caused by mutations in many different genes, what genetic concept does this illustrate?

Answer 69

Locus heterogeneity

Question 70

is an environmentally caused trait that mimics the appearance of a genetic disorder, but it is not inherited.

Answer 70

phenocopy