Chapter 2, Cell Cycle and Replication for Microanatomy

What is nondisjunction?

The failure of the homologous chromosome pairs to separate during the first meiotic division

What is anaphase lag?

Failure of two sister chromatids to separate during the second meiotic division (causing trisomies)

What common cytogenetic abnormalities cause commonly cause trisomies?

Anaphase lag

What are 3 other chromosomal abnormalities that can be detected by karyotyping?

Translocation

Abnormal chromosome structures

Amplification or deletion of parts of a chromosome

What sampling/methods can detect abnormalities?

Amniocentesis

Chorionic villous sampling

Cell free fetal DNA

What occurs during anaphase lag?

Gametes forms two copies of the chromosome (usually from the mother)

During fertilization, a third copy is added

What are some dysmorphic features of Down syndrome?

Epicanthic folds

Upslanting palpebral features

Low-set small ears

Flat facial profile

Short neck with excess skin

Furrowed tongue

Hypoplastic incurved 5th finger

Sandle toe-deformity

Single transverse palmar crease

Brushfield spots

Trisomy 18 is also known as:

Edward’s syndrome

What are some characteristics of Edward’s Syndrome?

Small head

Back of head is prominent

Ears are malformed and low set

Mouth and jaw are small (may have cleft lip/palate)

Hands are clenched into fists, and the index fingers overlaps with other fingers

Clubfeet, toes may be webbed or fused

Heart/lung abnormalities

Decreased muscle tone

Trisomy 13 is also known as:

Patau Syndrome

What are some characteristics of Patau Syndrome?

Kidney, heart, CNS malformations

Polydactyly

small head

Cleft lip or palate

Undescended or abnormal testes

Malformed ears

Typically die within the 1st year of life

How can Trisomy 13 be diagnosed?

By ultrasound

Maternal serum markers like alpha-fetoprotein

What is meiosis?

The process of sexual reproduction, involving the production of gametes

Meiosis can also be called:

Gametogenesis

Each gamete contains how many chromosomes (HAPLOID)?

23 chromosomes

What is fertilization?

Gametes fusing to form a zygote

When fertilization occurs, there are how many chromosomes (DIPLOID)?

46 chromosomes

What does the term ‘crossing over’ mean?

The mechanism that adds further genetic diversity

The mechanism of crossing over is called:

Chiasma formation (AKA PROPHASE 1)

What is an allele (alleles)?

Alternative forms of the same gene

The haploid gamete ends up with only how many chromosome pairs?

Only one of each

True or false: Each individual chromosome includes alleles from each parent.

TRUE

What occurs in the first meiotic division (MEIOSIS 1)?

1. Separation of homologous pairs of chromosomes

1. Each daughter cell contains a half complement of duplicated chromosomes

What occurs in the second meiotic division (MEIOSIS 2)?

1. Splitting of the chromatids (metaphase 2)

2. The chromatids migrate to opposite ends of the spindle (anaphase 2 and telophase 2)

Primitive germ cells of the male sex are:

Spermatogonia

After male maturity, the spermatogonia multiply continuously by:

Mitosis

Each male gamete undergoes a morphological development into mature:

Spermatozoon

Mitochondrial diseases present with what kind of characteristics?

Muscle weakness

Loss of coordination

Poor growth

Range of neurological symptoms

Autonomic dysfunction

Visual and hearing problems

What are a few examples of mitochondrial diseases?

Mitochondrial myopathies

Leber’s hereditary optic neuropathy

MERRF syndrome (Myoclonic epilepsy with ragged red fibers)

How is MERRF diagnosed?

A muscle biopsy, revealing the presence of “ragged red fibers”

How is Meiosis and Mitosis different?

Meiosis involves one reduplication of chromosomes, followed by two sequential cell divisions (a diploid cell producing four haploid germ cells)

Crossing over only occurs in meiosis (genetically different gametes)

Products of mitosis are GENETICALLY IDENTICAL

What is the main goal of mitosis?

Produce two genetically identical daughter cells for growth, repair, and asexual reproduction. Occurring in somatic cells