Unit c1: Cell division, genetics, and molecular biology

Question 1

apoptosis

Answer 1

programmed cell death. removes unwanted tissue and prevents cancer

Question 2

cell cycle

Answer 2

Interphase:
- G1 stage: growth
- S stage : synthesis of DNA
- G2 stage: growth
mitotic stage:
- Mitosis: division of nucleus
- Cytokinesis : division of the cytoplasm

Question 3

chromatid

Answer 3

One DNA molecule

Question 4

chromosome

Answer 4

Chromosomes are composed of chromatin.
* Chromatin is a combination of DNA and protein,
mostly histones.
Chromosomes are either:
Dispersed and extended in a non-dividing cell, so that
the DNA is available for gene expression
a) or
b) Condensed into compact, coiled form for cell division
* Histones play a role in tightly coiling the DNA

Question 5

cytokinesis

Answer 5

the division of the cytoplasm, follows mitosis. results in two daughter cells identical to the mother cell

Question 6

G1 stage

Answer 6

cell doubles its organelles and accumulates material for DNA synthesis

Question 7

G2 stage

Answer 7

cell synthesizes proteins for cell division

Question 8

interphase

Answer 8

is the stage of the cell cycle where the cell grows, carries out normal functions, and prepares for division by replicating its DNA. It consists of three phases: G₁ (growth), S (DNA synthesis), and G₂ (preparation for mitosis).

Question 9

mitosis

Answer 9

the division of the nucleus, follows interphase. sister chromatids separate into daughter chromosomes

Question 10

S stage

Answer 10

DNA synthesis occurs. DNA doubles. each chromosome changes from one DNA molecule to two identical DNA molecules

Question 11

somatic cell

Answer 11

body cells that continue to undergo cell division throughout life

Question 12

anaphase

Answer 12

Centromeres divide, and sister chromatids are moved
to opposite poles of the cell by spindle fibers

Question 13

cell plate

Answer 13

A structure in plant cells that forms during cytokinesis, eventually developing into the new cell wall between daughter cells.

Question 14

centrioles

Answer 14

A small, tube-like structure in animal cells that helps pull chromosomes apart during cell division.

Question 15

centromere

Answer 15

The part of a chromosome that holds the two sister chromatids together and helps them attach to spindle fibers during cell division.

Question 16

chromatin

Answer 16

Loose, thread-like DNA found in the nucleus that condenses into chromosomes during cell division.

Question 17

cleavage furrow

Answer 17

A groove that forms in animal cells during cell division, pinching the cell in half to create two new cells.

Question 18

diploid

Answer 18

A cell that has two sets of chromosomes, one from each parent (symbolized as 2n)

Question 19

DNA

Answer 19

A molecule that carries genetic information, found in the nucleus of cells, and determines an organism’s traits.

Question 20

haploid

Answer 20

A cell that has only one set of chromosomes, half the number of a diploid cell (symbolized as n).

Question 21

histones

Answer 21

Proteins around which DNA wraps to help organize and pack it into a compact structure called chromatin.

Question 22

metaphase

Answer 22

Spindle fibers are fully formed and attached to the
chromatids
* Centromeres of chromosomes are aligned at the
metaphase plate (the equator of the cell)

Question 23

metaphase plate

Answer 23

The imaginary line where chromosomes align during metaphase of cell division, preparing to be separated into daughter cells.

Question 24

nuclear envelope

Answer 24

The double membrane that surrounds and protects the nucleus in a cell, controlling what enters and exits.

Question 25

prophase

Answer 25

Nuclear envelope breaks apart; nucleolus begins to disappear * Chromatin condenses so that the chromosomes become visible * Each chromosome = two identical sister chromatids held together at the centromere * Spindle fibers begins to form between the centrioles and the centromeres

Question 26

spindle fibers

Answer 26

Protein structures that form during cell division and help separate chromosomes by attaching to their centromeres and pulling them apart.

Question 27

telophase

Answer 27

* Spindle fibers disappear * Daughter cells are forming * Nuclear envelope reappears * Nucleolus appears in each daughter cell nucleus Near the end of telophase: * Chromosomes turn back into chromatin * Cytokinesis (division of cytoplasm) begins

Question 28

crossing-over

Answer 28

A process during meiosis where homologous chromosomes exchange sections of their DNA, leading to genetic diversity in offspring.

Question 29

gametes

Answer 29

Reproductive cells (sperm in males and eggs in females) that have half the number of chromosomes, combining during fertilization to form a new organism.

Question 30

genetic variation

Answer 30

Differences in DNA among individuals in a population, which contribute to diversity in traits and help with adaptation to changing environments.

Question 31

homologous pair

Answer 31

A set of two chromosomes, one from each parent, that are similar in shape, size, and genetic content.

Question 32

independent assortment

Answer 32

The random distribution of different chromosomes into gametes during meiosis, leading to genetic variation.

Question 33

interkinesis

Answer 33

A short resting phase between meiosis I and meiosis II, where no DNA replication occurs.

Question 34

meiosis

Answer 34

A type of cell division that reduces the chromosome number by half, producing four genetically diverse gametes (sperm or egg cells).

Question 35

synapsis

Answer 35

The process during meiosis where homologous chromosomes pair up and align closely with each other.

Question 36

1 oocyte

Answer 36

An immature egg cell in females that is formed during fetal development and remains dormant until puberty, where it may resume development during ovulation.

Question 37

1 spermatocyte

Answer 37

An immature sperm cell that undergoes meiosis to eventually form four sperm cells. It is produced during male gamete development.

Question 38

2 oocyte

Answer 38

The egg cell formed after the primary oocyte undergoes the first division of meiosis. It is released during ovulation and can be fertilized by a sperm cell.

Question 39

2 spermatocyte

Answer 39

A cell formed after the primary spermatocyte undergoes the first division of meiosis. It will divide further to produce spermatids, which develop into sperm cells.

Question 40

dizygotic twins

Answer 40

Also known as fraternal twins, they are twins that develop from two separate eggs fertilized by two different sperm cells, resulting in genetically distinct siblings.

Question 41

monozygotic twins

Answer 41

Also known as identical twins, they are formed when a single fertilized egg splits into two embryos, resulting in genetically identical siblings.

Question 42

polar body

Answer 42

A small cell produced during the division of an oocyte (egg cell) that typically does not develop into a viable egg, and is reabsorbed by the body.

Question 43

sperm

Answer 43

The male reproductive cell responsible for fertilizing the female egg cell (ovum) to create a zygote. It carries half of the genetic material needed for reproduction.

Question 44

spermatid

Answer 44

– An immature male reproductive cell that results from the second division of meiosis. It develops into a mature sperm cell through a process called spermatogenesis.

Question 45

spermatogenesis

Answer 45

The process by which sperm cells are produced in the testes, involving the division and maturation of germ cells into mature sperm.

Question 46

zygote

Answer 46

The fertilized egg formed when a sperm cell from the male combines with an egg cell from the female, containing a full set of chromosomes (half from each parent).

Question 47

allele

Answer 47

Different forms of a gene that determine specific traits, such as eye color or blood type. Each individual has two alleles for each gene, one inherited from each parent.

Question 48

dihybrid cross

Answer 48

A genetic cross between two organisms that involves two traits, each with two alleles, to study how they are inherited together.

Question 49

dominant

Answer 49

An allele that expresses its trait even when only one copy is present, overpowering the effect of a recessive allele.

Question 50

F1 generation

Answer 50

The first generation of offspring produced from a cross between two parent organisms.

Question 51

F2 generation

Answer 51

The second generation of offspring, produced by breeding two individuals from the F1 generation. This generation shows the results of genetic recombination and segregation.

Question 52

gene

Answer 52

A segment of DNA that carries instructions for a specific trait or function, and is passed from parent to offspring.

Question 53

genotype

Answer 53

alleles that are responsible for an individual’s appearance

Question 54

heterozygous

Answer 54

If the two alleles are different, the individual is said to be heterozygous.

Question 55

homozygous

Answer 55

If the two alleles are the same, the individual is said to be homozygous

Question 56

law of independent assortment

Answer 56

A principle stating that genes for different traits are inherited independently of each other, meaning the inheritance of one trait doesn't affect the inheritance of another.

Question 57

law of segregation

Answer 57

Even though individuals have two alleles for each trait, their gametes only have one allele for each trait.

Question 58

locus

Answer 58

The specific location or position of a gene on a chromosome.

Question 59

monohybrid cross

Answer 59

A monohybrid cross is a genetic cross between two individuals that examines the inheritance of one specific trait. For example, if you're studying flower color, a monohybrid cross would focus only on how this single trait (flower color) is passed from parents to offspring. The parents could have different versions (alleles) of the gene for that trait, like purple or white. By tracking the inheritance of these alleles, we can predict the possible outcomes for the offspring's trait.

Question 60

phenotype

Answer 60

an individual’s appearance * may include physical, microscopic, and metabolic characteristics

Question 61

Punnett square

Answer 61

A diagram used to predict the genetic outcomes of a cross between two organisms, showing the possible allele combinations for offspring.

Question 62

recessive

Answer 62

An allele that only expresses its trait when two copies are present (one from each parent). It is masked by a dominant allele if only one is present.

Question 63

testcross

Answer 63

A genetic cross between an individual with an unknown genotype (but showing a dominant trait) and an individual with a homozygous recessive genotype, used to determine the unknown genotype.

Question 64

autosomal chromosomes

Answer 64

An autosomal chromosome is any chromosome other than the sex chromosomes (which are X or Y in humans).

Question 65

autosomal dominant disorder

Answer 65

A genetic disorder caused by a mutation in just one copy of a gene on an autosomal chromosome. Only one affected parent is needed to pass the disorder to their offspring. Examples include Huntington's disease and Marfan syndrome.

Question 66

autosomal recessive disorder

Answer 66

A genetic disorder that occurs when an individual inherits two copies of a mutated gene, one from each parent, on an autosomal (non-sex) chromosome. Examples include cystic fibrosis, sickle cell anemia, tay Sachs, phenylketonuria

Question 67

carrier

Answer 67

An individual who has one copy of a recessive allele for a genetic disorder but does not show symptoms of the disorder, as the dominant allele masks the effect. They can pass the allele to their offspring.

Question 68

pedigree

Answer 68

A pedigree is a chart of a family’s history with regards to a particular genetic trait .* Males are shown as squares  * Females are shown as circles  * Affected individuals are shaded ◼⚫

Question 69

sex chromosomes

Answer 69

The pair of chromosomes that determine an individual's sex. In humans, females typically have two X chromosomes (XX), and males have one X and one Y chromosome (XY).

Question 70

codominance

Answer 70

Codominance occurs when alleles are equally expressed in a heterozygote. * Example: roan cattle * Have areas of red fur and areas of white fur * Example: blood type AB * Has characteristics of both Type A and Type B blood (cow baby)

Question 71

incomplete dominance

Answer 71

Incomplete dominance occurs when the heterozygote has an intermediate phenotype between the two homozygotes. * Example 1: A curly-haired person reproduces with a straight-haired person. ➢ Their children will have wavy hair. * Example 2: Two wavy-haired people reproduce and have an expected offspring phenotypic ratio of 1:2:1. ➢ 1 curly hair: 2 wavy hair: 1 straight hair

Question 72

multiple allele inheritance

Answer 72

When a trait is controlled by multiple alleles, the gene exists as more than two alleles. * Example: There are the three alleles responsible for blood types in humans. IA = has A antigens on red blood cells * IB = has B antigens on red blood cells * i = has neither A nor B antigens on red blood cells * IA is dominant over i * IB is dominant over i * IA and IB are codominant

Question 73

polygenic inheritance

Answer 73

Polygenic inheritance occurs when a trait is governed by multiple genes. * Dominant alleles have a quantitative effect on the phenotype, and these effects are additive. * The result is a continuous variation of phenotypes. * An example of this is skin colour. * More than 100 different genes influence skin colour. * Other examples include height and weight.