Genetics and Genomics in Maternal Newborn Care

How many chromosomes do humans normally have?

46 chromosomes (22 pairs of autosomes + 1 pair of sex chromosomes)

What is a gene?

A segment of DNA on a chromosome that codes for a specific protein

What is aneuploidy?

An abnormal number of chromosomes (extra or missing)

What is trisomy?

Three copies of one chromosome

What is monosomy?

Only one copy of a chromosome instead of two

What type of cell division errors cause chromosomal anomalies?

Errors in mitosis or meiosis

What are the p arms of a chromosome?

The short arms

What are the q arms of a chromosome?

The long arms

What is the centromere?

The region that holds chromosome arms together and determines shape

What is the function of telomeres?

Protect chromosome ends during DNA replication

What maternal age increases risk for chromosomal anomalies?

Age > 35 years

Name three additional risk factors for aneuploidy.

Prior trisomy, smoking, radiation exposure, high BMI, possible folic acid deficiency

What is the most common survivable autosomal trisomy?

Trisomy 21 (Down syndrome)

What is the incidence of Down Syndrome?

1 in 700-800 births

How does maternal age affect Down syndrome risk?

Risk increases with maternal age, especially >35

Name classic physical features of Down syndrome.

Flat facial profile, upward-slanting eyes, short neck, small ears, protruding tongue, hypotonia, single palmar crease

What percentage of infants with Down syndrome have congenital heart defects?

About 50%

Why are infants with Down syndrome at increased aspiration risk?

Hypotonia, poor suck/swallow coordination, and congenital heart disease

How common are sex chromosome anomalies?

About 1 in 400 births

Turner syndrome occurs in which sex?

Females

What is the most common cause of primary amenorrhea?

Turner syndrome

Key features of Turner syndrome?

Short stature, webbed/wide chest, ovarian failure, infertility, cardiac and renal defects, lymphedema

Klinefelter syndrome occurs in which sex?

Males

Hallmark features of Klinefelter syndrome?

Tall stature, small testes, gynecomastia, infertility, delayed puberty

Triple X syndrome affects which sex?

Females

Common findings in Triple X syndrome?

Tall Stature, learning disabilities, delayed speech/motor skills, behavioral issues

What is multifactorial inheritance?

Disorders caused by multiple genes and environmental factors

Why is multifactorial inheritance hard to predict?

No clear inheritance pattern and strong environmental influence

How many mutated genes are needed for autosomal dominant disorders?

One

Give two examples of autosomal dominant disorders

Huntington disease, Marfan syndrome

How many mutated genes are needed for autosomal recessive disorders?

Two

Parents of a child with an autosomal recessive disorder are usually what?

Asymptomatic carriers

Examples of autosomal recessive disorders?

cystic fibrosis, sickle cell disease, PKU

What causes PKU (Phenylketonuria)?

Deficiency of phenylalanine hydroxylase (PAH)

Why is PKU dangerous if untreated?

Phenylalanine accumulates and causes brain damage

How is PKU treated?

Lifelong phenylalanine-restricted diet

How is PKU detected?

Newborn screening

Can cancer be inherited directly from parents?

No

What can be inherited related to cancer?

Genetic mutations that increase cancer risk

What does cell-free fetal DNA screen for?

Trisomy 21, 18, and 13

What does nuchal translucency measure?

Fluid at the back of the fetal neck

What are risks of chorionic villus sampling (CVS)?

Bleeding, infection, miscarriage, Rh sensitization

What does the quad screen measure?

AFP, hCG, estriol, inhibin-A

What conditions does the quad screen assess risk for?

Trisomy 21, trisomy 18, neural tube defects

When is the anatomy scan performed?

18–22 weeks gestation

What are the three components of newborn screening?

Heel-stick blood test, hearing screen, CCHD pulse oximetry