Teratogenic drugs inhibit crucial enzymes or receptors; however, they may not interfere with the formation of mitotic spindles or block energy production.

False

Theoretically, this means that each teratogen should have a “safe” dose, below which no teratogenesis occurs.

True

This drug was found not to be teratogenic in mice and rats but caused complex human malformations when many pregnant women ingested it in their first trimester of pregnancy.

Thalidomide

The fetus may possibly develop syphilis if the mother became infected in the 2 years before the pregnancy.

True

Positions of constriction in a chromosome.

Centromere

Using a stain such as Giemsa, chromosomes are classified according to their length and a certain structure called..

Centromere

The point at which the two identical strands of chromosomal DNA, called sister chro-matids, attach to each other during mitosis.

Centromere

The centromere is exactly in the middle.

Metacentric

The chromosome divides into a short arm (p, from French, petit) and a long arm (q, the next letter in the alphabet).

Submetacentric

A chromosome where the centromere is not central and is instead located near the end of the chromosome.

Acrocentric

Having the centromere at the end of the chromosome.

Telocentric

The Y chromosome is acrocentric.

True

These chromosome bands are highlighted using Giemsa stain

G bands

These chromosome bands stain with Giemsa and fluoresce when treated with quinacrine

Q bands

On appropriate staining, these chromosome bands present as reverse images of G and Q bands.

R bands

This is a method for staining centromeres and other portions of chromosomes containing constitutive heterochromatin.

C bands

Inactive X chromosome

Barr body

This technique stains the terminal ends of chromosomes.

T bands

The study of chromosomes and their abnormalities.

Cytogenetics

The current system of classification in cytogenetics.

International System for Human Cytogenetic Nomenclature

During normal meiosis, homologous chromo-somes (e.g., two chromosomes 1) form pairs, called..

Bivalents

Exchanges involving nonhomologous chromosomes

Translocation

Two major types of chromosomal translocation.

Robertsonian translocation, Reciprocal translocation

Refers to exchange of acentric chromosomal segments between different (nonhomologous) chromosomes.

Reciprocal translocation

A reciprocal translocation is balanced, regardless if there is loss of genetic material.

False

Balanced translocations are not generally associated with loss of genes or disruption of vital gene loci, so most carriers of balanced translocations are phenotypically nor-mal.

True

Balanced reciprocal translocations can be inherited for many generations.

True

Offspring of carriers of balanced translocations will have balanced karyotypes and may not show severe phenotypic abnormalities.

False

Also known as centric fusion, involves the centromere of acrocentric chromosome

Robertsonian translocation

Loss of a portion of a chromosome and involves either a ter-minal or an intercalary (middle) segment.

Chromosomal deletion

Name the chromosomal abnormalities depicted in the picture. Write your answer according to its order:

Deletion, Translocation, Inversion, Robertsonian translocation, Isochromosomal translocation, Ring formation

Disease associated with deletion

Cri du chat syndrome

Genetic disease which the short arm of chromosome 5 is deleted.

Cri du chat syndrome

Genetic disease associated with deletions in the short arm of chro-mosome 11.

Wilms tumor aniridia syndrome

A process in which a chromosome breaks at two points, the affected segment inverts and then reat-taches.

Chromosomal inversion

1. A type of chromosomal inversion which results from breaks on opposite sides of the centromere. 2. A type of chromosomal inversion which involves breaks on the same arm of the chromosome

Pericentric inversion, Paracentric inversion

Formed by a break involving both telomericends of a chromosome, deletion of the acentric fragments and end-to-end fusion of the remaining centric portion of the chromosome.

Ring chromosome

The most important clinical condition involving isochromosomes in which 15% of those affected have an isochromosome of the X chromosome.

Turner syndrome

Failure of paired chromosomes or chromatids to separate and move to opposite poles of the spindle at anaphase, during mitosis or meiosis.

Nondisjunction

Numerical chromosomal abnormal-ities arise primarily from nondisjunction.

True

The causes of chromosomal aberrations are largely known.

False

Most major chromosomal abnormalities are incompatible with life.

True

Up to 15% of spontaneous abortions have a chromosomal abnormality.

False

Karyotypes are described sequentially by:

Designation for short arm of chromosomes

Designation for long arm of chromosomes

Symbol for the addition and loss of chromosomal material respectively.

+, -

How is the loss (deletion) of part of a chromosome typically designated?

del

What is the notation for translocation in chromosomal aberrations?

t(brackets) or t followed by brackets containing the involved chromosomes

Numerical autosomal aberrations in liveborn infants are virtually all trisomies.

True

Karyotype for male with trisomy 21 (Down syndrome)

47, XY, +21

Karyotype for Female carrier of fusion-type translocation between chromosomes 14 and 21

45, XX,-14, -21 + t(14q21q)

Karyotype for Cri du chat syndrome (male) with deletion of a portion of the short arm of chromosome 5

46, XY, del(5p)

Karyotype for male with ring chromosome 19

46, XY, r(19)

Turner syndrome with monosomy X

45, X

Mosaic Klinefelter syndrome

46,XY/47,XXY

Trisomy 21 is the most common cause of mental retardation.

True

List some of the clinical features of Down Syndrome

Growth failure, Mental retardation, Flat occiput, Congenital heart disease, Dysplastic ears

Children with Down syndrome are invariably mentally retarded.

True

Also known as testicular dysgenesis, there are one or more X chromosomes beyond the normal male XY complement (XXY).

Klinefelter syndrome

This syndrome is a prominent cause of male hypogonadism and infertility.

Klinefelter syndrome

Also known as "supermale", is a genetic condition found in about 1 in 1000 male newborns, characterized by an extra Y chromosome, leading to features such as tall stature, cystic acne, and some motor and language development issues.

XYY male

The spectrum of abnormalities that results from complete or partial X chromosome monosomy in a phenotypic female.

Turner syndrome

Determined by two copies of the same gene, called alleles, located at the same locus on two homologous chromosomes.

Mendelian trait

Four Classifications of Mendelian Traits

Autosomal dominant, Autosomal recessive, Sex-linked dominant, Sex-linked recessive

These are traits or disorders that occur when a mutation is present in just one copy of a gene.

Autosomal dominant

These traits or disorders occur when both copies of a gene are present for a condition to be expressed.

Autosomal recessive

The trait must be present in both copies of the gene for a person to have the condition.

Sex-linked recessive

Mutation with replacement of one base by another

Point mutation

New codon with the mutation still codes for the same amino acid.

Synonymous mutation

Female preponderance, micrognathia, congenital heart disease, horseshoe kidney, deformed fingers

Chromosome 18 (47, XX or XY, +18: 1/8000)