Cell cycle, cell division and chromosome abnormalities

100 practice flashcards covering the cell cycle, mitosis, meiosis, gametogenesis, chromosomal abnormalities, and related topics from the lecture notes.

What are the four phases of the typical eukaryotic cell cycle?

G1, S, G2, and M.

What occurs during the S phase of the cell cycle?

DNA replication.

What is the role of the G1 checkpoint?

To ensure adequate resources, cell size, signals, and DNA integrity before entering S.

List the stages of mitosis in order.

Prophase, Prometaphase, Metaphase, Anaphase, Telophase (and cytokinesis).

What happens during prophase of mitosis?

Chromosomes condense and become visible; centrioles move apart; spindle forms.

What happens during prometaphase of mitosis?

Nuclear envelope breaks down; spindle fibers attach to kinetochores; chromosomes begin moving toward center.

What happens during metaphase of mitosis?

Chromosomes align on the metaphase plate with kinetochores attached to spindle fibers.

What happens during anaphase of mitosis?

Sister chromatids separate and move to opposite poles.

What happens during telophase of mitosis?

Chromosomes arrive at poles; nuclear envelope re-forms; cytokinesis begins.

What is cytokinesis?

Cytoplasmic division that produces two daughter cells.

What is meiosis?

Two sequential divisions producing haploid gametes with genetic recombination.

Name the prophase I stages of meiosis in order.

Leptotene, Zygotene, Pachytene, Diplotene, Diakinesis.

What is a tetrad?

A paired set of homologous chromosomes each consisting of two sister chromatids during prophase I.

What is crossing over?

Exchange of genetic material between non-sister chromatids of homologous chromosomes, increasing recombination.

What is a chiasma?

A visible site of crossing over between homologous chromosomes during diplotene.

What are dyads and monads in meiosis?

Dyads are two-chromatid structures after meiosis I; monads are single chromatids after meiosis II.

What are the products of meiosis II?

Four haploid gametes.

What is gametogenesis?

Process of forming mature gametes: spermatogenesis and oogenesis.

What is nondisjunction?

Failure of homologous chromosomes or sister chromatids to segregate properly during division.

What is euploidy?

Variation in complete chromosome sets; normal multiples of the haploid set.

What is monoploidy?

Having a single complete chromosome set (n).

What is polyploidy?

Having more than two complete chromosome sets (3N, 4N, etc.).

What is aneuploidy?

Abnormal number of chromosomes, not an exact multiple of the haploid set.

What is monosomy?

Loss of one chromosome: 2N−1.

What is trisomy?

Gain of one chromosome: 2N+1.

What is tetraploidy?

Four complete chromosome sets (4N).

What is a translocation?

Structural rearrangement where chromosome segments are exchanged between non-homologous chromosomes (reciprocal) or fused (Robertsonian).

What is deletion?

Loss of a chromosome segment.

What is duplication?

Gain of a chromosome segment present in addition to the normal copy.

What is inversion?

Chromosomal segment inverted 180 degrees; can be paracentric or pericentric.

What is a pericentric inversion?

Inversion that includes the centromere.

What is a paracentric inversion?

Inversion that excludes the centromere.

What is insertion?

Addition of a segment into a chromosome from another location.

What is an isochromosome?

Chromosome with two identical arms due to misdivision; unbalanced.

What is Robertsonian translocation?

Centric fusion of two acrocentric chromosomes, often reducing chromosome number.

What is reciprocal translocation?

Exchange of segments between non-homologous chromosomes.

What is tandem fusion?

End-to-end fusion of two chromosomes (a type of non-reciprocal rearrangement).

What is nondisjunction in meiosis I vs II?

Meiosis I: homologous chromosomes fail to separate. Meiosis II: sister chromatids fail to separate.

What zygotes can result from nondisjunction?

Monosomic (2N−1), disomic (2N), or trisomic (2N+1) after fertilization.

What is X monosomy fertility effect?

Sterility; variable signs such as abnormal estrus or underdeveloped ovaries.

What is XXX trisomy fertility effect?

Infertility; may have normal external genitalia with irregular estrus.

What is XXY trisomy fertility effect?

Sterility due to abnormal spermatogenesis; small testes.

What is XYY syndrome fertility effect?

Usually normal phenotype but small testes and infertility in some cases.

What are the cattle karyotype details cited?

2N = 60; X is submetacentric (SM); Y is metacentric (M).

What are the sheep karyotype details cited?

2N = 54; X is acrocentric (A); Y is metacentric (M).

What are the goat karyotype details cited?

2N = 60; X is acrocentric (A); Y is metacentric (M).

What are the pig karyotype details cited?

2N = 38; X is metacentric (M); Y is metacentric (M).

What are the horse karyotype details cited?

2N = 64; X is submetacentric (SM); Y is acrocentric (A).

What are the dog karyotype details cited?

2N = 78; X is submetacentric (SM); Y is metacentric (M).

What are the cat karyotype details cited?

2N = 38; X is metacentric (M); Y is metacentric (M).

What are the chicken sex chromosomes?

Males: ZZ; Females: ZW.

What does SM stand for in chromosome morphology?

Submetacentric.

What does A stand for in chromosome morphology?

Acrocentric.

What does M stand for in chromosome morphology?

Metacentric.

What are p and q arms?

p is the short arm and q is the long arm of a chromosome.

What is centromere?

Constriction point where sister chromatids are held together and spindle attaches during cell division.

What is zygotene?

Stage of prophase I where synapsis begins between homologous chromosomes.

What is pachytene?

Stage where homologous chromosomes are fully synapsed and crossing over occurs.

What is diplotene?

Stage where chiasmata become visible and crossing over completes.

What is diakinesis?

Final stage of prophase I; chromosomes condense and prepare for metaphase I.

What is Metaphase I?

Homologous chromosome pairs align at the metaphase plate; tetrads align.

What is Anaphase I?

Homologous chromosomes separate to opposite poles (reductional division).

What is Telophase I?

Two haploid sets form; cytokinesis occurs.

What is Meiosis II?

Equational division where sister chromatids separate, producing four haploid gametes.

What is spermatogenesis?

Process of sperm production from spermatogonia through meiosis and differentiation.

What is oogenesis?

Process of egg formation including meiosis and polar body formation.

What is spermatogonium?

Germ cell that divides to form spermatocytes; stem cell in spermatogenesis.

What is oogonium?

Germ cell that divides to form oogocytes; stem cell in oogenesis.

What is a primary spermatocyte?

Diploid cell that undergoes meiosis I to form two secondary spermatocytes.

What is a secondary spermatocyte?

Haploid cell formed after meiosis I; undergoes meiosis II.

What is a Spermatid?

Haploid cell that differentiates into mature spermatozoon.

What is an ovum?

Mature female gamete produced by oogenesis.

What is the first polar body?

Polar body extruded after meiosis I to reduce cytoplasm; accompanies oogenesis.

What is the second polar body?

Polar body extruded after meiosis II.

What is the role of chromosomal abnormalities in fertility?

They can reduce fertility or cause developmental defects; examples include aneuploidies and translocations.

What is the significance of X monosomy in fertility?

Often sterility with variable signs depending on species.

What is the significance of XXX trisomy in fertility?

Infertility with often normal external genitalia.

What is the significance of XXY trisomy in fertility?

Sterility due to impaired spermatogenesis.

What is the significance of XYY syndrome in fertility?

Often infertility; sometimes normal phenotype.

Which chromosomal rearrangement is common in cattle that fuses two acrocentric chromosomes?

Robertsonian translocation (centric fusion); e.g., joining of chromosome 1 and chromosome 29.

What is the effect of Robertsonian translocations on fertility?

Can be normal in carriers but often reduces fertility or alters litter sizes depending on carrier status.

Which translocation involves exchange between non-homologous chromosomes?

Reciprocal translocation.

What is the result of an X/autosome reciprocal translocation in pigs?

Females: normal phenotype but decreased litter size; males: abnormal spermatogenesis and sterility.

What is the result of a Y/autosome reciprocal translocation?

Males: abnormal spermatogenesis and sterility; rare.

What is a translocation X/Y?

Disorder of sex development and potential sterility.

What is the karyotype description for cattle in the provided notes?

2N=60; X SM; Y M.

What is the karyotype description for dogs in the provided notes?

2N=78; X SM; Y M.

What is the karyotype description for cats in the provided notes?

2N=38; X M; Y M.

What is the karyotype description for chickens in the provided notes?

2N=78; sex chromosomes Z and W (Males ZZ; Females ZW).