Basic Principles of Human Genetics Wksh. Flashcards
Material of heredity that is carried in the nucleus of each cell in the body
DNA
Body cells that divide by mitosis
Somatic cells
What do somatic cells provide?
Growth and development for tissue replacement and repair
Reproductive cells formed in the male/female gonads
Gametes
How do gametes reproduce?
Meiosis (contain 1/2 the genetic material of the parent cell)
What makes up the chromosomes?
22 matched pairs of autosomes that control most traits in the body
1 pair of sex chromosomes that determine sex and other secondary sexual traits
Each of the 23 pairs of chromosomes is ______ in terms of composition and traits regulated
Homologous or homozygous (matched)
Pictorial analysis of the number, size, and form of an individuals chromosomes
Karogram
How is a karogram taken?
From a blood sample
Chromosomes are stained and cut out and arranged in specific numeric order according to size.
How are the chromosomes of a karogram sample put in to determine the presence of gross chromosomal disorders? What does a normal karogram look like?
Put in groups A-G
Normal: 46XX or 46XY
What are 2 predisposing factors for occurrences of chromosomal abnormalities?
Advanced maternal age (over 35) and exposure to teratogens
What does it mean if there is an abnormal number of chromosomes?
More or less than required 46–can occur in the autosomes or the sex chromosomes
What is an example of a chromosomal abnormality that results in an extra chromosome?
Down Syndrome is an example of an extra chromosome on the 21st allele
What is trisomy?
The product of the union of a normal gamete with a gamete containing an extra chromosome—the result is an individual with 47 chromosomes in a cell
What is Kleinfelters?
An extra X on the sex chromosome—> a male but with feminine traits
Looks like XXY
If it is XYY it is a male with aggressive masculine traits
What is monosomy?
One chromosome of a pair is absent (only 45 chromosomes) in each cell
T/F: Missing an autosome may result in death of the embryo
True
The basic unit of heredity
Genes
What do genes determine?
Traits—every characteristic one possesses, from eye color to the disease passed on as a genetic trait to offspring!
Pair of genes coded the same for a particular trait
Homozygous
Pair of genes coded different for a particular trait
Heterozygous
Genes are ____ or _____ for a trait
Dominant or recessive
Characteristic that will be expressed in the individual even if its partner gene is different
Dominant
EX: Gene for brown eyes is dominant; gene for blue eyes is recessive
A person with one gene from each parent will have brown eyes
Characteristic will be expressed only if carried by both chromosomes of a pair
Recessive gene
EX: 2 genes for blue eyes are required for a person to have blue eyes; 2 genes for CF is required for offspring to inherit the disease
What kind of inheritance is this: Abnormal gene is dominant; a disorder is expressed when the dominant gene is present even if the other gene in a pair is normal
Autosomal dominant inheritance (mendalian)
What are some examples of autosomal dominant inheritance?
Polydacyly (extra digit)
Huningtons chorea
Achondroplasia (dwarfism)
Polycystic kidney disease
Who is affected more in autosomal dominant inheritance: males or females?
Equally affected
What kind of inheritance?
Both genes of a pair must be abnormal for a trait (disorder) to be expressed
Autosomal recessive inheritance
Autosomal recessive inheritance: Carriers of the trait (heterozygous individuals) are _____ but may pass the trait to offspring.
Unaffected clincially
Who is affected more in autosomal recessive inheritance: males or females?
Equally affected!
What are some examples of autosomal recessive inheritance?
Tay Sachs
SCA
CF
A defective recessive gene is carried on the X chromosome
X-linked recessive
Females are predominately carriers and males express the disorders when they receive the gene from their mother
What are examples of X-linked recessive diseases?
Color blindness
Hemophilia!!!!
Duchenne muscular dystrophy!!!!!
A defective dominant gene is carried on the X chromosome; expressed in both male and female offspring who inherit the defective gene
X-linked dominant
Absence or defect in enzymes responsible for the metabolism of fats, proteins, or carbs
Inborn errors of metabolism
What are examples of inborn errors of metabolism?
This leads to an accumulation of harmful substances–PKU is one
PKU test is mandatory in infants before they can leave the hospital
A pattern of inheritance reflecting the interaction of several genetic and environmental factors that create mild to severe defects
Multifactorial inheritance
What are examples of multifactorial inheritance?
Cleft lip
Cleft palate
NTD
Congenital heart disease
Genetic counseling may occur in many contexts and settings. Examples?
Prenatal clinic
Birthing unit
Well-child clinic
Family planning clinics
Agents that cause birth defects
Teratogens
The severity of defects from teratogens depend on what 3 things?
- Timing of exposure (organogenesis is most vulnerable time)
- Different susceptibility of organ systems
- Strength of causative agent
Teratogens: What are some examples of causative or suspected agents?
Maternal infection diseases Drugs and other substances Pollutants Radiation Maternal hypothermia Effects of maternal med disorders
Avoiding fetal exposure–This ideally begins before conception. What is our role for informing women about possible teratogenic infections?
- They need to get the rubella immunization prior to pregnancy (3 months or more)
- If titer is low, counsel women about situations to avoid
- Avoid changing cat liter boxes because they have parasites in them and that can cause toxoplasmosis
Avoiding fetal exposure: Drugs and other substances. What do we need to know about this to inform preg moms?
- There are pregnancy categories for meds
- X= DONT TAKE IT!!!!
- Women should eliminate use of non therapeutic drugs and alcohol
- It is difficult to establish the effects of illicit drugs
