Preconception and Genetics

sex linked disorders

have their origin on the X chromosomes - red green colorblindness - hemophilia - fragile X chromosome

autosomal recessive disorder

Two copies of the abnormal gene must be present for the disease or trait to develop; diagnosed in early infancy/early childhood ~ symptomatic - PKU - sickle cell disease - tay sachs disease - cystic fibrosis

When it is paired with another recessive gene for the same trait

Under what circumstances will a recessive gene be expressed?

bernice, age 45

Which of the following individuals has the greatest risk for bearing a child with trisomy 21?

The study of monozygotic twins is important because it helps us, to some extent, identify genetic versus environmental contributions to behavior.

Which of the following is true of identical twin studies?

Huntington's disease

Which of these genetic disorders usually does not express symptoms until adulthood?

phenotype

an individual's particular set of OBSERVED characteristics - What we see

trisomy's

Conditions in which a child has 3 copies of a specific autosome.

genotype

the unique genetic blueprint of each individual.. - Genetic makeup - Instructions for growth and development

recessive pattern

two recessive genes are necessary to produce an associated trait

Gametes contain only 23 chromosomes; other body cells contain 46.

what is the difference between gametes and all other body cells

the chromosomes of monozygotic twins are IDENTICAL and and fraternal twins are conceived with two eggs and two sperm

what is the difference between monozygotic and dizygotic twins

dominant pattern

pattern of inheritance in which a single dominant gene influences a person's phenotype

red green colorblindness

- 1 in 800 men are affected and 1 in 4000 women. - Trouble differentiating between the colors red and green.

cystic fibrosis

- Abnormal production of thick mucous that impacts the GI and Respiratory system. - 1000 cases diagnosed each year. - Caucasian babies are more likely to have cystic fibrosis than other ethnic groups

fragile x syndrome

- Affects 1 in 4000 males and 1 in 8000 females. X chromosome has a damaged spot. - Caused by recessive gene on X chromosome

Phenylketonuria (PKU)

- Baby has problems digesting phenylalanine, which results in toxins building up in the baby's brain causing mental retardation. - Occurs in about 1 in every 100,000 babies. - If the baby does not consume foods containing phenylalanine, he/she won't develop mental retardation. - Early diagnosis is critical. Milk is one of the foods the baby can't eat. - Most states require all newborns be tested soon after birth. - Caucasian babies are more likely to have PKU than other ethnic groups.

hemophilia

- Disorder in which the blood of affected individuals lacks the chemical components to clot. - Approximately 1 in 5000 baby boys have this disorder.

classical behavioral features of sex linked disorders

- Mild-to-severe cognitive impairment/normal IQ with learning disabilities - Delayed speech and language - Hyperactivity - Autistic-like behaviors - Aggressive behaviors

trisomy 13 and 18

- More severe and few children live past their first birthday. - Risk increases with maternal age. - Risk: Greatest risk mother greater than 35 yo. - Prognosis: few live past 1yo.

trisomy 21 - down syndrome

- Most common trisomy in which there are 3 copies of chromosome 21. - Occurs 1 in every 800 infants. - Distinctive features: smaller brains, physical abnormalities such as heart defects. - They have mental hinderances but can learn many skills.. - Risk increases with maternal age; greatest risk for mothers >35 years of age.. - Occurs more often in Caucasian than African-- - American families - Risk: Greatest risk mother greater than 35 yo. - Prognosis: Impaired mental function but can still function in society.

klinefeler's syndrome (XXY)

- Occurs in 1 out of every 500 males. - Physical Appearance: Normal appearance but may have underdeveloped testes and sperm counts. - At puberty experience male & female changes. i.e. penis enlargement and breast development (gynecomastia). - Cognitive Development Cognitive impairment w/ language delays - Behavioral issues, shyness & passivity Not related to maternal age.

turners (XO) - monosomy X

- Physical Development - Anatomically female but show stunted growth and are sterile. - About 90% require hormones to achieve menstruation and breast development at puberty. - Malformations of heart & kidneys. - Cognitive Development Perform poorly on tests that measure spatial ability. Normal or above performance on verbal skills. - Not related to maternal age.

tay sachs disease

- Results in severe mental retardation. - Very few children survive past 3 years of age. - Occurs in about 1 in 3000 babies born to Jewish couples of Eastern European ancestry.

sickle cell disease

- The blood can't carry enough oxygen to keep the body's tissues healthy due to red blood cell deformities. With early diagnosis and antibiotic tx, >90% of children with sickle cell survive to adulthood. - More common in West African and African American infants. - Almost ½ West Africans have sickle cell disease or sickle cell trait. - In the US 1 in 625 African Americans have sickle cell disease. 1 in 12 have sickle cell trait.

genomic imprinting

A chemical marker on a gene that may turn on or off normal development - a chemical label that identifies each gene in a person's body as having come from the father or mother - may be particularly important in diseases that appear later in life such as some types of cancer, Type II diabetes and heart disease

autosomal dominant disorders

Abnormal gene from one parent enough to inherit disease or trait - asymptomatic usually until adulthood - Huntington's disease - hypertension - schizophrenia - migraine headaches

homozygous

Individual carries either 2 dominant or 2 recessive genes

heterozygous

Individual carries one dominant and one recessive gene

polygenic inheritance

Many genes influence the phenotype. Blending of outcomes, blend to take from both dominant and recessive qualities - skin color - eye color - body type

Brown eyes

Skylar has brown eyes, thin lips, and curly blonde hair. Which of the following traits is polygenic?

X chromosome

The genes that cause sex-linked disorders are found on the...

23 pairs

The nucleus of the majority of typical human cells contains how many chromosomes?

karotyping

the process by which photographs of chromosomes are taken in order to determine the chromosome complement of an individual, including the number of chromosomes and any abnormalities - a test to examine chromosomes in a sample of cell - can help identify genetic problems as the cause of a disorder or disease