bio exam

Question 1

What is a DNA probe used for?

Answer 1

A DNA probe is a labeled DNA strand used to find specific DNA sequences; it helps detect mutations or genes in medical diagnostics.

Question 2

How might a researcher use a DNA probe?

Answer 2

To detect genetic disorders or identify specific genes in a sample, such as testing for BRCA1 mutations.

Question 3

What is CRISPR-Cas9?

Answer 3

A gene-editing tool that acts like “molecular scissors” to cut and edit DNA at specific locations.

Question 4

What is the purpose of cell division?

Answer 4

To grow, repair tissues, and replace dead or damaged cells.

Question 5

Why must DNA replicate before cell division?

Answer 5

So that each new cell gets an identical copy of DNA.

Question 6

What is semi-conservative replication?

Answer 6

Each new DNA molecule has one original strand and one new strand.

Question 7

What can happen if DNA replication has errors?

Answer 7

Mutations may occur, potentially leading to diseases like cancer.

Question 8

What is chromatin?

Answer 8

Uncoiled DNA and protein in the nucleus during interphase.

Question 9

Why must DNA condense into chromosomes before division?

Answer 9

To ensure accurate DNA separation into daughter cells.

Question 10

What happens in interphase?

Answer 10

The cell grows (G1), copies DNA (S), and prepares to divide (G2).

Question 11

What are the two main steps of cell division?

Answer 11

Mitosis (nuclear division) and cytokinesis (cytoplasm splits).

Question 12

What is the first sign of cytokinesis?

Answer 12

The formation of a cleavage furrow.

Question 13

Mitosis stages summary?

Answer 13

Chromosomes condense → align in center → sister chromatids separate → new nuclei form.

Question 14

What regulates the cell cycle?

Answer 14

Chemical checkpoints ensure proper division and repair DNA.

Question 15

What happens if cell division control is lost?

Answer 15

Uncontrolled cell growth (cancer).

Question 16

Benign vs. malignant tumors?

Answer 16

Benign = non-cancerous; Malignant = invasive and can spread.

Question 17

What is metastasis?

Answer 17

Spread of cancer cells to other parts of the body.

Question 18

Body’s defenses against cancer?

Answer 18

Immune system & tumor suppressor genes like p53.

Question 19

Causes of cancer?

Answer 19

DNA mutations from replication errors or mutagens (e.g. UV, smoking, inherited mutations like BRCA1).

Question 20

What does ‘diploid’ mean?

Answer 20

A cell with two sets of chromosomes (46 in humans).

Question 21

Where are chromosomes in diploid cells?

Answer 21

Inside the nucleus, arranged in pairs.

Question 22

What is a karyotype?

Answer 22

A visual display of all chromosomes arranged by size and type.

Question 23

Difference between autosomes and sex chromosomes?

Answer 23

Autosomes = chromosomes 1–22; Sex chromosomes = X and Y.

Question 24

What are homologous chromosomes?

Answer 24

Pairs with the same genes but possibly different alleles.

Question 25

What is the only non-homologous pair?

Answer 25

X and Y chromosomes in males.

Question 26

Why are gametes haploid?

Answer 26

So the zygote has the correct number (46); otherwise, it would double.

Question 27

What is meiosis?

Answer 27

A process that reduces chromosome number by half to form haploid gametes.

Question 28

Meiosis I vs. Meiosis II?

Answer 28

I = homologous chromosomes separate; II = sister chromatids separate.

Question 29

Final result of meiosis?

Answer 29

4 haploid cells with genetic variation.

Question 30

How does meiosis create genetic variation?

Answer 30

Through crossing over, independent assortment, and random fertilization.

Question 31

What is crossing over?

Answer 31

Homologous chromosomes exchange DNA during Prophase I.

Question 32

What is independent assortment?

Answer 32

Random alignment of chromosomes during Meiosis I.

Question 33

How does random fertilization increase diversity?

Answer 33

Any sperm can fertilize any egg → many combinations.

Question 34

Why is every zygote genetically unique?

Answer 34

Due to variation from crossing over, assortment, and fertilization.

Question 35

What is nondisjunction?

Answer 35

Failure of chromosomes to separate properly during meiosis.

Question 36

Result of nondisjunction?

Answer 36

Gametes with too many or too few chromosomes.

Question 37

What is trisomy?

Answer 37

An extra chromosome (e.g. Trisomy 21 = Down syndrome).

Question 38

Why is missing a chromosome more harmful than having an extra?

Answer 38

The body tolerates extra DNA better than missing essential genes.

Question 39

Compare meiosis and mitosis.

Answer 39

Mitosis = 1 division, 2 identical cells for growth/repair; Meiosis = 2 divisions, 4 different haploid cells for reproduction.

Question 40

Where is sperm made?

Answer 40

In the seminiferous tubules of the testes.

Question 41

Sperm pathway?

Answer 41

Testes → vas deferens → urethra → penis (fluids from prostate & seminal vesicles).

Question 42

Hormones regulating sperm?

Answer 42

Testosterone and FSH control sperm production.

Question 43

Where are eggs produced?

Answer 43

In the ovaries (oogenesis).

Question 44

Egg pathway to uterus?

Answer 44

Ovary → uterine tube → uterus → (possibly out the vagina if unfertilized).

Question 45

How long are egg and sperm viable?

Answer 45

Egg = ~24 hours; Sperm = ~5 days.

Question 46

What is shed during menstruation?

Answer 46

The endometrium (uterine lining).

Question 47

Which hormones spike during ovulation?

Answer 47

LH and FSH.

Question 48

What builds the uterine lining?

Answer 48

Progesterone.

Question 49

Compare spermatogenesis vs. oogenesis.

Answer 49

Sperm = many small cells, continuous; Eggs = one large cell/month, limited.

Question 50

How do hormonal contraceptives work?

Answer 50

They prevent ovulation by mimicking estrogen/progesterone.

Question 51

What do chromosomes do?

Answer 51

Carry genes that pass traits from parent to offspring.

Question 52

Gene vs. allele vs. chromosome?

Answer 52

Gene = trait unit, allele = version of gene, chromosome = DNA bundle.

Question 53

Who was Gregor Mendel?

Answer 53

“Father of Genetics” who studied inheritance using pea plants.

Question 54

Dominant vs. recessive alleles?

Answer 54

Dominant = shows if present; recessive = masked unless both alleles are recessive.

Question 55

Heterozygous vs. homozygous?

Answer 55

Hetero = different alleles; Homo = same alleles.

Question 56

Genotype vs. phenotype?

Answer 56

Genotype = gene combo; Phenotype = physical trait.

Question 57

What is a monohybrid cross?

Answer 57

Inheritance pattern of one trait (e.g. Aa x Aa → 3:1 ratio).

Question 58

Incomplete dominance vs. codominance?

Answer 58

Incomplete = blend (red + white = pink); Codominance = both show (AB blood type).

Question 59

Pleiotropy?

Answer 59

One gene affects multiple traits.

Question 60

What is polygenic inheritance?

Answer 60

Traits influenced by many genes (e.g. height, skin color).

Question 61

How does the environment affect traits?

Answer 61

External factors like nutrition or sunlight can influence gene expression.