Biol20A final 🥶

Compare and contrast how prokaryotic and eukaryotic cells reproduce asexually

Eukaryotic cells reproduce asexually through mitosis, while prokaryotic cells reproduce asexually through binary fission. Binary fission is simpler and faster.

Describe the levels of chromatin packaging that organize and protect eukaryotic genomes

DNA wraps around histones to form nucleosomes, nucleosomes coil to form chromatin fiber, chromatin fiber condenses into chromosomes.

Name the major stages of the eukaryotic cell cycle and describe what happens during each stage

Interphase (G1, S, G2): G1 and G2 is normal cell growth and S is when DNA duplicates Prophase: Chromosomes condense, nuclear envelope starts to break down, spindle fibers emerge from centrosomes, centrosomes move to opposite poles Prometaphase: chromosomes continue to condense, kinetochores appear at the centromeres, mitotic spindle microtubules attach to kinetochores, nuclear envelope finishes breaking down Metaphase: Chromosomes line up at the metaphase plate and a spindle fiber attaches to each sister chromatid Anaphase: Centromeres split in two, spindle fibers pull the chromosomes apart, spindle fibers elongate the cell Telophase: Chromosomes arrive at opposite ends of the cell, nuclear envelope surrounds each set of chromosomes, mitotic spindle breaks down, spindle fibers continue to push poles apart Cytokinese: Cell physically separates into two daughter cells

Describe the physical changes that occur during each stage of mitosis

Prophase: Chromosomes condense, nuclear envelope starts to break down, spindle fibers emerge from centrosomes, centrosomes move to opposite poles Prometaphase: chromosomes continue to condense, kinetochores appear at the centromeres, mitotic spindle microtubules attach to kinetochores, nuclear envelope finishes breaking down Metaphase: Chromosomes line up at the metaphase plate and a spindle fiber attaches to each sister chromatid Anaphase: Centromeres split in two, spindle fibers pull the chromosomes apart, spindle fibers elongate the cell Telophase: Chromosomes arrive at opposite ends of the cell, nuclear envelope surrounds each set of chromosomes, mitotic spindle breaks down, spindle fibers continue to push poles apart Cytokinese: Cell physically separates into two daughter cells

Recognize and draw eukaryotic cells in each stage of cell division

Prophase: chromosomes condensed just floating around, metaphase: lined up at the plate, anaphase, being pulled apart by spindle fibers, telophase cleavage forms

Compare and contrast cytokinesis in animal and plant cells

In animal cells a cleavage furrow forms that eventually separates the cell into two daughter cells. In plant cells a cell plate forms that separates the cell into two daughter cells.

Explain how cyclins, cyclin-dependent kinases, and cell-cycle checkpoints regulate cell division

Cyclins are regulatory proteins whose levels fluctuate throughout the cell cycle. Cyclin-dependent kinases (CDKs) are enzymes that become active when bound to cyclins. These cyclin-CDK complexes push the cell through different stages of the cell cycle. Cell-cycle checkpoints ensure that conditions are correct (e.g., DNA is undamaged and fully replicated) before the cell proceeds.

Asexual reproduction

A form of reproduction where cells reproduce independently and create identical daughter cells

Clone

Identical daughter cell

Binary fission

The process by which prokaryotic cells go through asexual reproduction. DNA replicates and then moves to each side of the cell and then the membrane pinches and the cell is split into two

Cell cycle

The series of events in which a cell grows, replicates DNA, and divides

Chromosome

A package of DNA that consists of genes

Chromatin

protein-DNA complex that serves as the chromosomes' building material

Histones

Histones are positively charged proteins that DNA wraps around to form nucleosomes, helping package DNA into chromatin and condense it into chromosomes during cell division

Nucleosomes

Nucleosomes are the basic units of chromatin

Metaphase chromosome

A fully condensed chromosome that consists of two identical sister chromatids joined together at the centromere during metaphase of mitosis

Interphase (G1, S, G2, G0)

G1 is normal cell growth, G2 is preparing for mitosis, G0 is a state where mitosis won’t happen, and S is where DNA duplicates

Mitosis

The process by which cells produce identical daughter cells.

Prophase

Chromosomes condense, nuclear envelope breaks down, spindle fibers emerge from centrosomes, centrosomes move to opposite poles

Prometaphase

Chromosomes continue to condense, kinetochores appear at the centromeres, mitotic spindle microtubules attach to kinetochores

Metaphase

Chromosomes line up at the metaphase plate and a spindle fiber attaches to each sister chromatid

Anaphase

Centromeres split in two, spindle fibers pull the chromosomes apart, spindle fibers elongate the cell

Telophase

Chromosomes arrive at opposite ends of the cell, nuclear envelope surrounds each set of chromosomes, mitotic spindle breaks down, spindle fibers continue to push poles apart

Cytokinesis

Cell physically separates into two daughter cells

Nucleolus

The membrane of the nucleus, breaks down during prophase

Chromatid

One of the sister chromatids, which are identical chromosomes joined together by a centromere

Sister chromatids

Identical chromosomes joined together by a centromere

Telomere

The protective caps on chromosomes

Centromere

Region of chromosome where sister chromatids are joined

Mitotic spindle

Structure made of microtubules that moves chromosomes

Metaphase plate

The center line of the cell where chromosomes line up at during metaphase

Contractile ring

A ring of actin located below the cell membrane that is responsible for creating the cleavage furrow

Cleavage furrow

In animal cells during cytokinesis the indent that forms in the membrane when starting two separate the cell into two cells

Cell plate

The structure made by plants during cytokinesis to separate the two new daughter cells into individual cells

Cyclin Cyclin-dependent kinase (cdk)

Cyclins bind to and activate CDKs, forming complexes that regulate progression through the cell cycle

M-promoting factor

A cyclin-Cdk complex that trigger a cell’s passage past the G2 checkpoint into the M phase

Cell cycle checkpoint

Checkpoints throughout the cell cycle to make sure that the cell is doing mitosis correctly

Explain the differences between haploid and diploid cells and organisms.

Haploid cells only have one of the chromosomes that would form a homologous pair while diploid cells have both chromosomes so they have a set of homologous chromosomes.

Describe how prokaryotic cells divide by binary fission.

The DNA replicates and then it kinda moves over to the opposite sides of the cell and the membrane pinches to create two different cells

Explain the differences between homologous and non-homologous chromosomes.

Homologous chromosomes are the same genes but with different alleles while non-homologous chromosomes have different genes.

Describe the chromosome composition of human cells.

Humans have 23 pairs of homologous chromosomes which makes 46 total chromosomes

Compare and contrast haplontic and diplontic lifecycles.

Haplontic is when the majority of an organism’s lifecycle has haploid cells and diplontic is when the majority of an organism's lifecycle has diploid cells.

Describe the major differences between asexual and sexual reproduction, including their sources of genetic variation.

Asexual reproduction creates clones while sexual reproduction creates genetic variety. The sources of genetic variety in asexual reproduction are mutations while the sources of genetic variety in sexual reproduction is recombination, independent assortment, and random fertilization.

Illustrate how a diploid cell with at least two pairs of homologous chromosomes generates haploid cells via meiosis.

A diploid starts meiosis with pairs of homologous chromosomes, and then during anaphase I the homologs separate so each haploid daughter cell has one pair of sister chromatids. During anaphase II the sister chromatids separate so each daughter cell has one chromatid.

Explain how independent assortment and recombination contribute to genetic diversity using clearly labeled diagrams.

Independent assortment allows for 2²³ combinations of alleles in each gamete and recombination allows for even more.

Haploid

A cell with only one set of chromosomes (no homologous pairs)

Diploid

A cell with homologous chromosomes

Homologous chromosome

Two chromosomes that code for the same gene but can contain different alleles

Non-homologous chromosome

Chromosomes that don’t code for the same gene

Alleles

Different versions of the same gene that code for the same type of trait but with different variations

Somatic cell

A non-sex cell

Germ cell

A sex cell

Egg

The sex cell produced by a female

Sperm

The sex cell produced by a male

Karyotype

The diagram that maps out the human chromosomes

Autosome

Not related to sex

Sex chromosome

The X or Y chromosome (in humans) that determines sex

Gamete

The haploid sex cell produced at the end of meiosis

Zygote

A fertilized diploid cell

Meiosis

The process of creating genetically diverse haploid gametes through sexual reproduction

Meiosis I

The first phase of meiosis where pairs of homologous chromosomes are separated to create two haploid cells that each have one pair of sister chromatids

Meiosis II

The second phase of meiosis where two haploid cells with sister chromatids separate to create four haploid daughter cells with one chromatid in each

Prophase 1

Chromosomes pair so they’re in pairs of sister chromatids and then crossing over occurs

Metaphase 1

Homologous chromosomes line up at the metaphase plate (independent assortment)

Anaphase 1

Homologous chromosomes separate

Telophase 1

Cell starts to cleave into two daughter cells

Prophase 2

Chromatin condenses, nuclear envelope condenses, spindle fibers reform

Metaphase 2

Sister chromatids line up at the metaphase plate

Anaphase 2

Sister chromatids are pulled apart by spindle fibers

Telophase 2

Cell starts to cleave so that each new daughter cell has one chromatid

Independent assortment

When homologous chromosomes line up in metaphase there’s a 50/50 chance for which homologous chromosome lines up on what side

Synapsis Recombination (crossing over)

During prophase I, homologous chromosomes overlap and switch alleles

Parental chromosome

Chromosome unchanged by recombination

Recombinant chromosome

A chromosome that differs from the parents because of crossing over

Describe some of the early theories of heredity and how they differ from our current knowledge of how genetic traits are transmitted from one generation to the next.

Early theories like blending inheritance suggested traits mix together, and inheritance of acquired characteristics suggested traits gained during life could be passed on.

Explain the relationship between alleles, genes (DNA) and chromosomes.

Genes are segments of DNA and alleles are different versions of the same gene that codes for a different trait and chromosomes are packages of genes.

Explain how the results of Mendel’s monohybrid crosses led him to propose the principle of segregation.

Mendel saw a 3:1 ratio in the F2 generation, showing that alleles separate during gamete formation so each gamete gets one allele.

Explain how the results of Mendel’s dihybrid crosses led him to propose the principle of independent assortment.

Mendel saw a 9:3:3:1 ratio in the F2 generation, showing that alleles of different genes assort independently during gamete formation.

Explain how the behavior of chromosomes during meiosis leads to the segregation and independent assortment of alleles into gametes

Chromosomes are pulled to opposite poles in a way where only one chromosome is pulled (segregation) and then out of the homologous chromosomes it’s random which one chromosome will be put on which side of the metaphase plate so it’s a 50/50 chance for which chromosome gets pulled to each side.

Define linkage and explain how it affects the segregation of alleles into gametes

Genes that are closer together on a chromosome have a higher chance of being inherited together because there’s a lower chance that crossing over will separate them

Explain how recombination affects the segregation of linked genes during meiosis

Recombination is less likely to happen on genes that are closer together on the same chromosome so they’re more likely to be inherited together

Describe how sex-linkage influences the transmission of genetic traits

Genes that are located on the X or Y chromosome will have their inheritance pattern impacted by the fact that female offsprings have two X chromosomes while males only have one so they’re more likely to have recessive X-linked diseases.

Explain the molecular basis of incomplete dominance

The dominant allele by itself doesn’t completely mask the effect of the recessive allele

Explain how polygenic inheritance and environment effects complicate genetic studies

Polygenic inheritance involves multiple genes contributing to a single trait, resulting in continuous variation (e.g., height). Environmental factors can influence how genes are expressed, further affecting the phenotype.

Blended inheritance

Hypothetical inheritance pattern where parental traits are blended together in the offspring to produce an intermediate physical appearance

Inheritance of acquired characteristics

A discredited biological hypothesis suggesting that physical changes acquired by an organism during its lifetime—through use or disuse—can be passed on to its offspring

Particulate theory of heredity

States that traits are inherited through discrete, indivisible units (now known as genes) rather than through blending fluid

Gregor Mendel

a diva who is like the founding father of genetics bc he experimented with pea plants

Mendelian genetics

The study of heredity and alleles

True-breeding

Organisms that produce offspring with the same phenotype consistently over generations when self-pollinated or bred with others of the same genotype (will be homozygous recessive or dominant)

Monohybrid cross

A cross focusing on one gene so like a cross between Aa x aa

Dihybrid cross

A cross focusing on two genes so like a cross between AaBb x aaBB

Test cross

Crossing an unknown genotype with a homozygous recessive organism to see what traits are bred to determine the unknown genotype

Alleles

Different variations of the same gene that could for different variations of the same trait

Homozygous

Having two of the same alleles

Heterozygous

Having two different alleles

Dominant

Only one dominant allele is needed to show that trait

Recessive

Both recessive alleles are needed to show that trait

Genotype

The combination of alleles that an organism has

Phenotype

The traits that an organism expresses