genetics

Question 1

define the central dogma of molecular biology and name the two processes that are involved in the flow of genetic information

Answer 1

-the flow of genetic information from DNA to RNA to protein
-transcription (DNA to RNA) and translation (RNA to protein)

Question 2

Describe how the information in DNA is used to produce specific proteins and can ultimately determine the characteristics of an individual organism

Answer 2

-DNA’s information, encoded in the sequence of nucleotides, dictates protein production through transcription and translation, ultimately determining an organism’s characteristics by influencing the types and functions of the proteins it produces.
-the process where a cell uses a DNA sequence (a gene) to create an RNA molecule
-the process by which a cell makes proteins using the genetic information carried in messenger RNA (mRNA)

Question 3

Describe the structure of DNA and explain how it stores genetic information

Answer 3

-double stranded helix
-stores genetic information through the specific sequence of four nitrogenous bases (adenine, thymine, guanine, and cytosine) strung along a sugar-phosphate backbone

Question 4

Describe the process of transcription, including which molecules serve as templates, which molecules are produced, and what enzyme is involved.

Answer 4

-a gene’s DNA sequence is copied (transcribed) to make an RNA molecule, using RNA polymerase to synthesize a complementary RNA strand from a DNA template.
-a DNA molecule serves as the template for the synthesis of a complementary RNA molecule
- a single-stranded RNA molecule
-RNA polymerase

Question 5

Describe the process of translation, including which molecules serve as templates, which molecules are produced, and what cellular machinery is involved.

Answer 5

-a cell uses the genetic information encoded in messenger RNA (mRNA) to synthesize proteins, involving ribosomes, mRNA, and transfer RNA (tRNA
-messenger RNA (mRNA
-proteins (specifically, polypeptide chains which then fold into functional proteins)
-ribosomes, tRNA, and mRNA, work together to synthesize proteins by decoding the genetic code from mRNA into a specific sequence of amino acids.

Question 6

universal genetic code

Answer 6

-Adenine goes with Thymine
-Guanine goes with Cytosine

Question 7

which molecule contains codons

Answer 7

messenger RNA (mRNA)

Question 8

which molecule “reads” them

Answer 8

a ribosome

Question 9

which molecule contains anticodons

Answer 9

transfer RNA (tRNA) molecules

Question 10

how do anticodons and codons interact

Answer 10

through complementary base pairing, ensuring the correct amino acid is added to the growing polypeptide chain

Question 11

Define the term mutation and describe the effects of mutations on protein structure and function.

Answer 11

a heritable change in an organism’s DNA sequence, which can alter the amino acid sequence of a protein, potentially affecting its structure and function, and ultimately the organism’s phenotype.

Question 12

Explain the difference between the genotype and the phenotype of an individual.

Answer 12

The genotype refers to an organism’s genetic makeup (the specific genes and alleles it carries), while the phenotype is the observable physical or biochemical characteristics resulting from the interaction of that genotype with the environment.

Question 13

Distinguish and define the terms gene, allele, and locus

Answer 13

A gene is a unit of heredity that codes for a specific trait or protein, while an allele is a specific variant of that gene. A locus (plural: loci) refers to the specific location of a gene on a chromosome.

Question 14

Define the terms homozygous and heterozygous as they apply to genotypes; be able to identify and provide examples of genotypes of each type

Answer 14

homozygous refers to having two identical alleles for a specific gene, while heterozygous means having two different alleles for that gene.

Question 15

Describe how a mutation in DNA can result in a phenotypic change.

Answer 15

altering the function of genes, which in turn impacts the production and function of proteins, ultimately affecting an organism’s characteristics.

Question 16

Describe how the single mutation responsible for the disease sickle cell anemia results in the disease symptoms.

Answer 16

The single mutation responsible for sickle cell anemia causes a change in the hemoglobin protein, leading to abnormally shaped red blood cells that can’t carry oxygen efficiently and block blood flow, resulting in various symptoms.

Question 17

Describe how chromosomes, genes, and alleles are passed on from parents to offspring and the role of meiosis in this process of inheritance.

Answer 17

Each parent contributes half of their genetic material (one set of 23 chromosomes) in the form of gametes (sperm and egg), which fuse during fertilization, restoring the full set of chromosomes and creating a unique combination of genes and alleles in the offspring.

Question 18

Explain how the formation of haploid gametes in meiosis contribute to variability of offspring during sexual reproduction

Answer 18

it allows for the mixing and shuffling of genetic material from two parents, resulting in unique combinations of genes in each offspring.

Question 19

Explain how the segregation of alleles contribute to variability of offspring during sexual reproduction

Answer 19

During sexual reproduction, the segregation of alleles (different versions of a gene) during meiosis and the random combination of gametes (sperm and egg) during fertilization contribute significantly to the genetic variability of offspring.

Question 20

Explain how the independent assortment of chromosomes contribute to variability of offspring during sexual reproduction

Answer 20

creating a vast number of possible combinations of maternal and paternal chromosomes in each gamete, leading to unique genetic makeup in each offspring.

Question 21

the number of cells produced in meiosis

Answer 21

four genetically unique, haploid daughter cells from a single parent cell.

Question 22

the ploidy level of the resulting cells in meiosis

Answer 22

the ploidy level of cells is reduced from diploid (2n) to haploid (n) during the process, resulting in four haploid daughter cells from a single diploid parent cell.

Question 23

the number of times DNA is replicated in meiosis

Answer 23

only once

Question 24

number of cell divisions in meiosis

Answer 24

two successive rounds of cell division, meiosis I and meiosis II

Question 25

Identify the steps of meiosis

Answer 25

-prophase, metaphase, anaphase, telophase, and cytokinesis

Question 26

describe the major events of prophase

Answer 26

the cell's chromosomes condense, becoming visible, the nuclear envelope breaks down, and the mitotic spindle begins to form.

Question 27

describe the major events of metaphase

Answer 27

the nucleus dissolves and the cell's chromosomes condense and move together, aligning in the center of the dividing cell

Question 28

describe the major events of anaphase

Answer 28

the sister chromatids of each chromosome, which were previously joined at the centromere, separate and are pulled towards opposite poles of the cell by spindle fibers, ensuring each daughter cell receives a complete set of chromosomes.

Question 29

describe the major events of telophase

Answer 29

the chromosomes arrive at the poles, the nuclear envelope reforms around each set of chromosomes, the nucleoli reappear, and the spindle fibers disassemble,

Question 30

describe the major events of cytokinesis

Answer 30

the cytoplasm splitting into two, resulting in two daughter cells,

Question 31

define chromosome and explain how it relates to meiosis and gamete formation

Answer 31

-Chromosome: A DNA-containing structure that carries genetic information in the form of genes. -Relation to Meiosis: Meiosis halves the number of chromosomes, ensuring gametes have only one set (23 in humans). -Relation to Gamete Formation: Gametes (sperm and egg) are formed through meiosis and each gets one chromosome from each pair.

Question 32

define chromatid and explain how it relates to meiosis and gamete formation

Answer 32

-Chromatid: One of two identical halves of a duplicated chromosome, joined at the centromere. -Relation to Meiosis: During meiosis I, chromatids stay together. In meiosis II, sister chromatids are pulled apart into separate gametes. -Relation to Gamete Formation: The separation of chromatids ensures each gamete gets the correct amount of DNA.

Question 33

define homologous chromosomes and explain how it relates to meiosis and gamete formation

Answer 33

-Homologous Chromosomes: A pair of chromosomes—one from each parent—that have the same genes in the same order but may have different versions (alleles). -Relation to Meiosis: In meiosis I, homologous chromosomes pair up and then separate, reducing the chromosome number by half. -Relation to Gamete Formation: This separation ensures each gamete gets only one chromosome from each pair, contributing to genetic diversity.

Question 34

define centromere and explain how it relates to meiosis and gamete formation

Answer 34

-Centromere: The region of a chromosome where two sister chromatids are joined and where spindle fibers attach during cell division. -Relation to Meiosis: In meiosis I, centromeres hold sister chromatids together as homologous chromosomes separate. In meiosis II, centromeres split to allow sister chromatids to separate. -Relation to Gamete Formation: Proper centromere function ensures chromosomes are divided accurately, so each gamete gets the correct genetic material.

Question 35

define diploid and explain how it relates to meiosis and gamete formation

Answer 35

-Diploid: A cell that has two sets of chromosomes—one from each parent (46 total in humans). -Relation to Meiosis: Meiosis starts with a diploid cell and reduces it to haploid cells by halving the chromosome number. -Relation to Gamete Formation: Diploid cells undergo meiosis to form haploid gametes (sperm or egg), which ensures the correct chromosome number is restored at fertilization.

Question 36

define haploid and explain how it relates to meiosis and gamete formation

Answer 36

-Haploid: A cell that has only one set of chromosomes (23 in humans). -Relation to Meiosis: Meiosis produces haploid cells from a diploid cell by reducing the chromosome number in half. -Relation to Gamete Formation: Gametes (sperm and egg) are haploid, so when they fuse during fertilization, they form a diploid zygote with the correct number of chromosomes.

Question 37

genotype

Answer 37

the genetic makeup of an organism

Question 38

phenotype

Answer 38

the observable characteristics or traits of an organism

Question 39

state the law of segregation of alleles and explain what it means

Answer 39

-Law of Segregation of Alleles: Each individual has two alleles for each gene, and these alleles separate during meiosis so that each gamete gets only one allele. -What it means: When forming sperm or egg cells, an organism passes on only one of its two alleles for each trait. This explains why offspring inherit one allele from each parent.

Question 40

state the law of independent assortment and explain what it means.

Answer 40

-Law of Independent Assortment: Genes for different traits can separate independently during the formation of gametes. -What it means: The inheritance of one trait (like eye color) doesn’t affect the inheritance of another trait (like hair color), as long as the genes are on different chromosomes. This increases genetic variation in offspring.

Question 41

Distinguish between dominant and recessive alleles and understand the effects of dominance/recessiveness on phenotypic ratios (as opposed to genotypic ratios).

Answer 41

-Dominant Allele: An allele that shows its effect even if only one copy is present -Recessive Allele: An allele that only shows its effect if two copies are present -Phenotypic Ratio: Dominant alleles mask recessive ones, so in a cross like Aa × Aa, the phenotypic ratio is 3 dominant : 1 recessive. -Genotypic Ratio: The same cross gives a genotypic ratio of 1 AA : 2 Aa : 1 aa.

Question 42

monohybrid cross

Answer 42

only comparing one gene

Question 43

dihybrid cross

Answer 43

compares two genes

Question 44

examples of variation from Mendelian ratios caused by genetic linkage.

Answer 44

-Linked Genes: Genes located close together on the same chromosome tend to be inherited together, not assorting independently as Mendel predicted. -Result: The ratios deviate from Mendelian predictions because linked genes don’t follow the law of independent assortment unless crossing over separates them.

Question 45

define sex chromosome and autosome and explain how they relate to gamete formation and sex determination.

Answer 45

-Sex Chromosome: A chromosome that determines an organism’s sex (X and Y in humans). -Autosome: Any chromosome that is not a sex chromosome (humans have 22 pairs of autosomes). -Relation to Gamete Formation: Gametes get one sex chromosome and one copy of each autosome. Sperm can carry either an X or a Y chromosome; eggs always carry an X. -Relation to Sex Determination: If a sperm carrying an X fertilizes the egg → XX = female. If a sperm carrying a Y fertilizes the egg → XY = male.

Question 46

Understand and recognize examples of variation from Mendelian ratios caused by sex linkage.

Answer 46

-Sex-linked traits are usually found on the X chromosome, since it carries more genes than the Y chromosome. -Males (XY) have only one X chromosome, so a single recessive allele on the X will show the trait. -Females (XX) need two copies of the recessive allele to show the trait; if they have one, they’re carriers. -Typical Mendelian cross (Aa × Aa) gives a 3:1 phenotypic ratio. Sex-linked cross (carrier female × normal male) gives: Sons: 50% affected, 50% normal Daughters: 50% carriers, 50% normal This is not a 3:1 ratio and varies by sex, showing its non-Mendelian.

Question 47

Understand and recognize examples of the variation from Mendelian ratios caused by incomplete dominance.

Answer 47

-occurs when neither allele is completely dominant over the other. The heterozygous phenotype is a blend of the two homozygous phenotypes. -Phenotypic Ratio in Incomplete Dominance: Cross: RW × RW Genotypes: 1 RR : 2 RW : 1 WW Phenotypes: 1 Red : 2 Pink : 1 White (1:2:1 phenotypic ratio) instead of the 3:1 seen in classic Mendelian dominance -Incomplete dominance changes both genotypic and phenotypic ratios to 1:2:1

Question 48

Understand and recognize examples of the variation from Mendelian ratios caused by codominance.

Answer 48

-occurs when both alleles are fully expressed in a heterozygous individual. The result is not a blend, but both traits appearing together. -Phenotypic Ratio in Codominance: Cross: IAIB × IAIB Possible offspring phenotypes: A, B, AB The phenotypic and genotypic ratios vary, but codominant traits are both visible in heterozygotes -How to Recognize It: Both parental traits are clearly visible in the offspring. No blending, unlike incomplete dominance. Heterozygotes show a combination, not an intermediate -Codominance causes both alleles to be expressed equally in the phenotype, leading to patterns like AB blood type or roan coloration — not a single, mixed color or trait.

Question 49

Understand the relationship between the phenomena of genetic linkage and crossing-over and the consequences of genetic linkage on gene segregation in gametes and formation of recombinant phenotypes of the offspring.

Answer 49

-Genetic Linkage: When genes are located close together on the same chromosome, they are said to be linked and tend to be inherited together. -Crossing-Over: During meiosis I, homologous chromosomes exchange segments. This process can break the linkage between genes, creating new allele combinations. -Relationship Between the Two: Linked genes don’t follow the law of independent assortment. Crossing-over provides a way for linked genes to recombine, increasing genetic diversity. -Consequences for Gene Segregation and Offspring: Without Crossing-Over: Linked genes are passed on together in the same combinations as the parents. Fewer unique combinations (fewer recombinant types). With Crossing-Over: Some gametes receive recombinant chromosomes (new gene combinations). This leads to recombinant phenotypes in offspring — combinations not seen in either parent. -Linked genes → inherited together more often -Crossing-over → creates recombinant phenotypes, breaking linkage -This causes variation from Mendelian ratios, especially fewer recombinants than expected if the genes were assorting independently.

Question 50

level of biological organization at which microevolution occurs

Answer 50

population

Question 51

Define the term microevolution and understand how population genetics can be used to study it

Answer 51

-the change in allele frequencies within a population over time. -Population genetics is the study of how genes (alleles) behave in populations. It uses mathematical models (like the Hardy-Weinberg equation) to: Track changes in allele and genotype frequencies Identify evolutionary forces (e.g., selection, mutation, drift) Predict future genetic changes

Question 52

population

Answer 52

A group of individuals of the same species that live in the same area and can interbreed.

Question 53

gene pool

Answer 53

The total collection of alleles (gene versions) present in all individuals of a population.

Question 54

Define and be able to calculate allele frequency.

Answer 54

-Allele frequency is the proportion of a specific allele (version of a gene) in a population's gene pool. -frequency of A (p)= number of A alleles/total number of alleles -frequency of a (q)= number of a alleles/ total number of alleles -p+q=1

Question 55

Define and be able to calculate genotype frequency

Answer 55

-Genotype frequency is the proportion of individuals in a population with a specific genotype (like AA, Aa, or aa). -number of individuals with a genotype/total number of individuals

Question 56

difference between genotype frequency and allele frequency.

Answer 56

-genotype: Measures frequency of genotypes like AA, Aa, or aa. Based on individuals. Adds up to 1 -allele: Measures frequency of individual alleles like A or a. Based on total number of alleles. Each allele adds up to 1

Question 57

Define the term Hardy-Weinberg Law and know what is meant by the term Hardy-Weinberg Equilibrium

Answer 57

-The Hardy-Weinberg Law states that allele and genotype frequencies in a population will remain constant from generation to generation unless acted upon by evolutionary forces (like mutation, selection, or drift). -A population is in Hardy-Weinberg Equilibrium (HWE) when allele and genotype frequencies stay the same over time, meaning no evolution is occurring. -Conditions for HWE (no evolution): No mutations, No natural selection, No gene flow (migration), Random mating, Large population size (no genetic drift) -p^2+2pq+q^2=1 -p+q=1 -p² = frequency of AA -2pq = frequency of Aa -q² = frequency of aa

Question 58

State the difference between a population in Hardy-Weinberg Equilibrium and one undergoing microevolution.

Answer 58

-Hardy-Weinberg Equilibrium: Allele and genotype frequencies stay constant, No evolution is occurring, Assumes ideal conditions (no mutation, selection, etc.), Used as a baseline for detecting genetic changes -Microevolution: Allele frequencies change over time, Evolution is occurring within the population, Results from forces like mutation, natural selection, gene flow, genetic drift, or non-random mating, Shows actual changes in population genetics -If a population deviates from Hardy-Weinberg expectations, it is undergoing microevolution.

Question 59

Using phenotype frequencies, be able to estimate allele frequencies if you assume that a population is in Hardy-Weinberg Equilibrium.

Answer 59

-p=1-q -If you’re given the frequency of a recessive phenotype, start with q², then find q, and use p + q = 1

Question 60

Define the term mutation and describe how it can contribute to microevolution.

Answer 60

-A mutation is a change in the DNA sequence of an organism’s genome. -How It Contributes to Microevolution: Mutations create new alleles, increasing genetic variation in a population. If a mutation affects traits related to survival or reproduction, natural selection may favor or eliminate it. Over time, mutations can change allele frequencies, leading to microevolution. -Mutations are the original source of all genetic variation, making them essential for evolutionary change at the population level.

Question 61

Define the term gene flow and describe how it can contribute to microevolution.

Answer 61

-Gene flow is the movement of alleles from one population to another through migration and interbreeding. -How It Contributes to Microevolution: Introduces new alleles into a population, increasing genetic diversity. Can change allele frequencies, especially if large numbers of individuals migrate. May make populations more genetically similar or introduce traits that affect survival and reproduction. -Gene flow is a source of genetic change and contributes to microevolution by mixing genetic material between populations.

Question 62

Define the term genetic drift and describe how it can contribute to microevolution.

Answer 62

-Genetic drift is the random change in allele frequencies in a population, especially in small populations. -How It Contributes to Microevolution: Causes allele frequencies to shift by chance, not by natural selection. Can lead to loss of genetic variation, even eliminating alleles completely. May result in genetic differences between populations over time. -Genetic drift causes random evolution, especially in small populations, and contributes to microevolution without regard to an allele’s advantage or disadvantage.

Question 63

Define the term selection and describe how it can contribute to microevolution.

Answer 63

-Selection is the process where certain traits become more or less common in a population due to their impact on an organism’s survival and reproduction. -How It Contributes to Microevolution: Individuals with advantageous traits are more likely to survive and pass on their genes. Over time, favorable alleles increase in frequency. This causes directional changes in allele frequencies, leading to microevolution. -Types of Selection: Natural selection: Driven by environmental pressures. Sexual selection: Driven by traits that improve mating success. Artificial selection: Human-directed breeding for specific traits. -Selection is a non-random force that shapes populations by increasing beneficial alleles and is a major driver of microevolution.

Question 64

Identify which of the microevolutionary forces act at random (with no direction).

Answer 64

-mutation -gene flow -genetic drift

Question 65

Define the terms reproductive isolating mechanism and biological species concept and describe how the former can lead to the process of speciation.

Answer 65

-A species is a group of organisms that can interbreed and produce fertile offspring in nature but are reproductively isolated from other such groups. -A reproductive isolating mechanism is a biological barrier that prevents gene flow between populations, keeping them from breeding successfully. -Types of Reproductive Isolation: Prezygotic (before fertilization): Temporal isolation (different mating times), Behavioral isolation (different courtship behaviors), Mechanical isolation (incompatible reproductive organs), Gametic isolation (incompatible sperm/egg) Postzygotic (after fertilization): Hybrid inviability (offspring don’t survive), Hybrid sterility (offspring are infertile) -How It Leads to Speciation: If populations are reproductively isolated, they accumulate genetic differences over time. Eventually, they become distinct species—a process called speciation. Isolation stops gene flow, allowing independent evolution.