Chapter 2: Chromosomes and Cellular Reproduction

bacteria and archaea

what two domains are prokaryotes?

eukaryotes, archaea, and bacteria

what are the 3 domains of life?

archaea and eukaryotes

what are the two most closely related domains of life?

they are acellular

why do viruses not fit in the tree of life?

usually 1 circular molecule; double stranded

describe the genome of bacteria and archaea

multiple linear molecules

describe the genome in eukaryotes

plasmids

small, extrachromosomal DNA molecule within a cell that is physically separated from chromosomal DNA and can replicate independently

organellar DNA

the genetic material found in certain cell organelles, primarily mitochondria (in all eukaryotes) and chloroplasts (in plants and algae), separate from the DNA in the cell's nucleus

DNA + histone

? + ? = chromatin

chromatin

the complex of DNA and proteins (mainly histones) that forms chromosomes inside the cell nucleus, acting as an organized package to fit long DNA strands into a small space while also controlling gene activity

packs a lot of DNA into a small nucleus

what is the benefit of having histones?

some do and some don’t

do some archaea have histones?

gene

the basic unit of heredity; contains a code for proteins that help to build and maintain and organism

chromosome

thread-like structures in the nucleus of cells, made of DNA tightly coiled around proteins (histones) that package and organize genetic instructions

diploid

containing two complete sets of chromosomes, one from each parent

homologous

pairs of chromosomes in diploid organisms (like humans) that are similar in size, shape, and gene arrangement, with one inherited from each parent, carrying the same genes at the same locations (loci) but potentially different versions

haploid, triploid, octoploid

what are some examples of other ploidy levels?

46

how many chromosomes do humans have?

telomere

protective caps of repetitive DNA and proteins at the ends of chromosomes

centromere

constricted region on a chromosome that acts as the attachment point for spindle fibers during cell division, ensuring sister chromatids separate equally into daughter cells

origin of replication

a specific DNA sequence where DNA duplication begins, serving as the starting point for unwinding the double helix

kinetochore

multiprotein complex acting as the attachment site for spindle microtubules (the "ropes" of the cell) during cell division (mitosis and meiosis) to ensure sister chromatids are pulled apart accurately to opposite daughter cells

spindle microtubules

protein fibers responsible for chromosome movement

chromatids

two identical, thread-like strands that make up a single, duplicated chromosome, joined at the centromere

binary fission

how do prokaryotes reproduce?

cell growth and development and cell cycle checkpoints

what occurs during interphase?

nuclear and cell division

what occurs during M phase?

G1/S and G2/M

what are the two checkpoints during the cell cycle?

prevents the formation of tumors

why are checkpoints important during the cell cycle?

checkpoints

crucial quality control mechanisms that halt cell division to ensure proper completion of each stage

interphase

the longest period of the cell cycle

cell growth and protein synthesis necessary for cell division

what is occurring during the G1 gap during interphase?

no cell division or growth

what occurs in the G0 phase of interphase?

stay indefinitely or return to G1

what two things can happen to cells if they enter G0?

no

are all enzymes necessary for cell division present during the G1/s checkpoint?

duplication of chromosomes (DNA synthesis)

what occurs during the S phase of interphase?

true

T/F: DNA synthesis must precede mitosis

cohesin

what holds sister chromatids together at the end of S phase?

cohesin

ring-shaped protein complex that acts as molecular "glue," holding sister chromatids together after DNA replication to ensure proper chromosome separation during cell division

biochemical reactions and final prep for cell division

what occurs during the G2 phase of interphase?

is DNA completely replicated and damage-free

what is the G2/M checkpoint looking for?

diploid to diploid, no genetic variation, sister chromatids separate, and produces genetically identical daughter cells

what are the general characteristics of mitosis?

2 rounds; round 1 is diploid to haploid and where genetic variation occurs, round 2 is haploid to haploid and sister chromatids separate

what are the general characteristics of meiosis?

condensation of chromosomes and formation of the mitotic spindle

what are the key events in prophase of mitosis?

microtubules

protein polymers that begin to form the mitotic spindle

centriole

Centrioles are microtubule-derived structures that are essential to form centrosomes; serve as an anchoring point

condensins

protein that helps to condense chromosomes

chromosomes align on metaphase plate, centrosomes center at spindle poles, and spindle-assembly checkpoint

what are the key events of metaphase (mitosis)?

ensures proper tension at kinetochore

what is the function of the spindle-assembly checkpoint during metaphase of mitosis?

proper attachment of microtubules

what generates tension at the kinetochore?

sister chromatids separate and daughter chromosomes move to opposite spindle poles

what are the key events of anaphase (mitosis)?

separase

enzyme that breaks down cohesin

molecular motors

remove tubulin from the microtubules, shortening them and causing chromosomes to move away

chromosomes arrive at spindle poles, nuclear membrane reforms into 2 nuclei into one cell, chromosomes relax and lengthen, and cytokinesis

what are the key events in telophase (mitosis)?

cytokinesis

the final step in cell division where the cytoplasm physically divides to form two separate daughter cells

no

does chromosome number reduce during telophase (mitosis)?

no

has genetic variation been generated during telophase (mitosis)?

split roughly even

how do cytoplasm and other organelles get divided during telophase (mitosis)?

meiosis

cell division that results in the production of gametes

genetic variation

why does sexual reproduction matter?

chromosomes condense and the spindle forms, homologs pair, and crossover occurs

what are the key events of prophase I?

chiasmata

where does crossover occur during prophase I?

diploid and lined up in pairs along the metaphase plate

describe how the chromosomes are lined up during metaphase I?

remain attached and travel as a pair

how do sister chromatids travel during anaphase I?

shugosin

what protein protects chromosome arms at the centromere?

no

are sister chromatids identical to one another during anaphase I?

diploid to haploid

how does ploidy change during telophase I?

yes

is genetic variation created during telophase I?

chromosomes arrive at spindle poles and cell divides

what happens during telophase I?

interkinesis

brief resting period between mitosis and meiosis where the nuclear membrane reforms, spindle breaks down, and chromosomes relax

interkinesis is reversed

what happens during prophase II?

haploid and single file

what is the chromosome alignment during metaphase II?

no

does ploidy change during meiosis II?

4

how many cells do we end meiosis with?

prophase I and metaphase I

where is genetic variation introduced during meiosis?

spermatogenesis

sperm formation occurring in the testes

spermatogonium

undifferentiated male germ cell; diploid

primary spermatocyte

a large, diploid male germ cell in the testes that begins meiosis; diploid

secondary spermatocyte

haploid cells in the male testes that form after a diploid primary spermatocyte divides during the first stage of meiosis

spermatids

the haploid male gamete that results from division of secondary spermatocytes; can become sperm after maturation

sperm

male reproductive cells

continuous

is spermatogenesis a continuous or paused process?

oogenesis

egg formation occurring in the ovaries

oogonium

an immature female reproductive cell that gives rise to primary oocytes by mitosis; diploid

primary oocytes

an immature female germ cell, formed before birth, that begins meiosis but pauses in prophase I within an ovarian follicle; diploid

secondary oocyte

an immature egg cell released from the ovary during ovulation, formed from a primary oocyte after meiosis I; haploid

polar body

each of the small cells which bud off from an oocyte at the two meiotic divisions and do not develop into ova.

ovum

a mature female reproductive cell, especially of a human or other animal, which can divide to give rise to an embryo usually only after fertilization by a male cell

prophase I

where are primary oocytes arrested?

ovulation

monthly release of an egg from the ovary

fertilization

union of an egg and a sperm, leading to the development of a zygote

meiosis and fertilization

what two processes are required for sexual reproduction?

38

how many chromosomes do ligers have?

yes

is it possible for ligers to be fertile?