Mitosis and Meiosis Lecture Review

A set of practice flashcards covering mitosis, meiosis, Mendelian genetics, and the chromosomal basis of inheritance from lecture notes.

What is the genome of a cell?

All the DNA in a cell makes up the genome.

What is the difference between heterochromatin and euchromatin in eukaryotes?

Heterochromatin is highly condensed chromatin where genes are not active, while euchromatin is less condensed and contains active genes.

What are the names of the two arms of a chromosome?

The P arm, which is usually the short arm, and the Q arm, which is the long arm.

How many chromosomes are found in human somatic cells and human gametes respectively?

Human somatic cells have $46$ chromosomes, and human gametes have $23$ chromosomes.

What occurs during the S phase of interphase?

The cell copies its chromosomes so that daughter cells receive identical copies of the genetic material.

In what type of cells do centrosomes occur?

Centrosomes only occur in animal cells.

What is the metaphase plate?

An imaginary structure at the midway point between the spindle's two poles where chromosomes line up during metaphase.

How do chromosomes move to opposite ends of the cell during anaphase?

The microtubules shorten by depolymerising at the kinetochore end, physically pulling the chromosomes apart.

What structure forms in animal cells during cytokinesis to pinch the cell in two?

A contractile ring of microfilaments that forms a cleavage furrow.

How do prokaryotes reproduce?

They reproduce by binary fission, which starts with the replication of a single circular DNA molecule.

Which cell cycle checkpoint is generally considered the most important?

The G1 checkpoint.

What is the non-dividing state called that a cell enters if it does not receive a go-ahead signal at the G1 checkpoint?

The G0 phase.

What two components make up the Mitosis promoting factor (MPF)?

A cyclin-dependent kinase and a protein subunit called a cyclin.

What is density-dependent inhibition?

A physical signal where cells stop dividing once they cover a single layer.

What is the name of the woman from whom the HeLa cancer cell line was originally taken?

Henrietta Lacks.

What is metastasis?

The spread of cancer cells from the original site to locations distinct from it, forming secondary tumours.

How does the chemotherapy drug Taxol affect dividing cells?

It freezes the mitotic spindle by preventing its shortening, stopping cells from proceeding past metaphase.

What is a gene's locus?

A specific location on a certain chromosome where a gene is located.

Define homologous chromosomes.

A pair of chromosomes that have the same number, length, centromere position, staining pattern, and genes at the same loci.

What is a karyotype?

A display of the number, sizes, and shape of an entire set of chromosomes.

What does ploidy refer to?

The number of chromosome sets in a cell, represented by the letter $n$.

What are chiasmata?

The points of attachment where crossover occurred between non-sister chromatids.

What are the products of oogenesis in mammals?

One large haploid egg containing most of the cytoplasm and three polar bodies.

What are recombinant chromosomes?

Chromosomes that carry DNA from two different parents as a result of crossing over.

What is the formula used to calculate the possible number of different gametes produced by independent assortment?

$2^n$, where $n$ represents the number of homologous pairs of chromosomes.

What was the phenotypic ratio observed by Mendel in the F2 generation of a monohybrid cross for flower colour?

$3:1$, with three purple flowers for every one white flower.

What is a testcross?

A cross with a homozygous recessive genotype used to identify if an individual with a dominant phenotype is homozygous or heterozygous.

Define co-dominance.

A relationship between alleles where a heterozygote displays the phenotype of both alleles, such as the AB blood group.

What is epistasis?

When the phenotypic expression of one gene at one locus alters the expression of another gene at a second locus.

Which scientist provided the first evidence that genes are located on chromosomes using fruit flies?

Thomas Hunt Morgan.

What is a Barr body?

The inactive X chromosome in female mammals that condenses during embryonic development.

What does one centimorgan ($cM$) represent on a linkage map?

A $1\%$ recombination frequency.

What is aneuploidy?

The presence of an unusual number of chromosomes in a zygote resulting from non-disjunction.

What chromosomal condition causes Down syndrome?

Trisomy $21$, the presence of three copies of chromosome $21$, resulting in $47$ total chromosomes.

What is the Philadelphia chromosome?

A specific translocation between chromosomes $9$ and $22$ that is associated with chronic myeloid leukaemia.

What are the stages of the cell cycle?

The stages include G1 (gap 1), S (synthesis), G2 (gap 2), and M (mitosis and cytokinesis).

What role does the G2 checkpoint play in the cell cycle?

It checks for DNA damage and ensures that all chromosomes have been replicated successfully before mitosis.

Define binary fission.

A method of asexual reproduction in prokaryotes where a single cell divides into two identical daughter cells.

What structure is responsible for the separation of sister chromatids during mitosis?

The spindle apparatus, which includes microtubules that attach to kinetochores on the chromatids.

Explain the term synapsis in meiosis.

The pairing of homologous chromosomes during prophase I, forming tetrads and allowing crossover.

What is the significance of crossing over during meiosis?

It increases genetic variation by exchanging genetic material between non-sister chromatids of homologous chromosomes.

What is a monohybrid cross?

A genetic cross between parents that differ in one trait, determining the inheritance pattern of that trait.

What are the characteristics of cancer cells?

They exhibit uncontrolled growth, loss of differentiation, ability to invade other tissues, and often evade apoptosis.

What is a karyotype used for?

A karyotype is used to analyze the number and structure of chromosomes to identify genetic disorders.

Describe the role of cyclins in the cell cycle.

Cyclins are proteins that regulate the timing of the cell cycle by activating cyclin-dependent kinases (CDKs).

What is the difference between a genotype and a phenotype?

A genotype is the genetic constitution of an organism, while a phenotype is the observable physical traits resulting from the genotype.

Define the term haploid.

A cell with one complete set of chromosomes, represented as $n$, such as gametes.

What does the term autosomes refer to?

Chromosomes that are not involved in determining the sex of an organism, typically the first 22 pairs in humans.

What is gene linkage?

Gene linkage refers to genes that are located close together on the same chromosome and tend to be inherited together.

What is the purpose of a pedigree chart?

A pedigree chart is used to trace the history and inheritance of traits within a family across generations.

How does the drug Tamoxifen work in cancer treatment?

Tamoxifen acts as a selective estrogen receptor modulator (SERM), blocking estrogen receptors on breast cancer cells.

What is the role of tumor suppressor genes?

Tumor suppressor genes encode proteins that help regulate cell growth and division; mutations can lead to cancer.

Explain the difference between dominant and recessive alleles.

Dominant alleles express their trait even if only one copy is present, while recessive alleles require two copies to express the trait.

What is the significance of the 3:1 phenotypic ratio in Mendelian genetics?

It indicates that in a monohybrid cross, one trait is dominant over another, resulting in three individuals displaying the dominant phenotype for every one that displays the recessive phenotype.

Define polygenic inheritance.

A mode of inheritance where multiple genes influence a single trait, resulting in a continuous range of phenotypes.