Genetics and Genetic Disorders

Question 1

Know the 3 types of drug tolerance

Answer 1

Pharmacodynamic tolerance

Drug becomes less sensitive/responsive (e.g. receptor concentrations change)

Associated with long-term administration of drugs such as morphine and heroin

Tachyphylaxis

Reduction in drug responsiveness brought on by repeated dosing over a short time

Metabolic (pharmacokinetic) tolerance

Results from accelerated drug metabolism

Question 2

Know, in general term, how a protein is made; know general structure of DNA/RNA

Answer 2

During transcription, the info stored in a gene’s DNA is transferred to a similar molecule called RNA in the cell nucleus. mRNA contains the information for making a protein and it carries that message from the DNA out of the nucleus and into the cytoplasm. IN the cytoplasm, the mRNA interacts with a ribosome, which reads the mRNA’s sequence of bases. Each sequence of 3 bases (codons) code for one particular amino acid, which is the building block of proteins. The transfer RNA or tRNA assembles the proteins one amino acid at a time until the ribosome encounters the STOP codon and then the protein folds into itself and becomes the protein we know.

DNA is made up of molecules called nucleotides. Each nucleotide has a phosphate group, a sugar group and a nitrogen base (A, T, G, C). A and G are purines, C and T are pyrimidines. The DNA is found as a double helix composed of 2 chains of nucleotides held together by hydrogen bonds.

RNA is basically the same EXCEPT that the base thymine (T) is replaced by uracil (U) and ribose replaces the deoxyribose (sugar group), also it is single stranded and has a shorter chain of nucleotides

Question 3

Know what are chromosomes and how many humans have

Answer 3

Chromosomes:

a threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes.

How many do humans have:

In humans, each cell normally contains 23 pairs of chromosomes, for a total of 46. Twenty-two of these pairs, called autosomes, look the same in both males and females. The 23rd pair, the sex chromosomes, differ between males and females.

Question 4

Linkage

Answer 4

¨Two genes that are close together on the chromosome are called “linked”

¨Linked genes are rarely separated by crossing-over and therefore are usually inherited together

Question 5

Alleles

Answer 5

Copies of a gene

Question 6

Phenotype

Answer 6

a person’s physical characteristics

Question 7

Genotype

Answer 7

a person’s genetic material

Question 8

Recessive

Answer 8

If a trait is only expressed in a homozygote, it is recessive

Question 9

Dominant

Answer 9

If the trait is expressed on a heterozygous it is dominant

Question 10

Homozygous

Answer 10

Having two identical alleles at corresponding loci on homologous chromosomes

Question 11

Heterozygous

Answer 11

Having two different alleles at corresponding loci on homologous chromosomes

Question 12

Autosomes

Answer 12

Any chromosome not considered as a sex chromosome, or is not involved in sex determination

Question 13

Carrier

Answer 13

is a person or other organism that has inherited a recessive allele for a genetic trait or mutation but does not display that trait or show symptoms of the disease

Question 14

Epigenetics

Answer 14

the study of changes in organisms caused by modification of gene expression rather than alteration of the genetic code itself

Question 15

Mutagen

Answer 15

is a substance or agent that causes an increase in the rate of change in genes. Examples of mutagens include certain biological and chemical agents as well exposure to ultraviolet light or ionizing radiation.

Mutagenesis is the formation of mutations

Question 16

Know what a single-gene disorder is and know the various ways its passed onto offspring; know the types of mutations; know the single-gene disorders covered in lecture

Answer 16

Change of a single gene

Results in single protein or enzyme not being produced or having an altered function

Can have trivial or lethal effects depending on gene involved

Mutations

Can effect one or both autosomal gene pair

Can also affect sex-linked chromosomes

Follow mendelian pattern of inheritance: Gregory Mendel - punnett square

Question 17

How to pass it onto offspring

Answer 17

Autosomal dominant: non sex, phenotype is shown. When the dominant gene holds the mutation holding a 50% the offspring will get it.

Aa and aa. A is dominant a is recessive. Showing below is a 50% chance of giving it to offspring.

A a

Silent mutations:

Change in a base pair that does not result in a change in the sequence of amino acids in a protein. The protein is still the same.

“ the fat cat saw the red dog”

Missense mutation:

A change in an amino acid where the new amino acid has a different property than the old amino acid.

The protein with the new primary structure may have altered, reduced or no activity. Can make it not viable or malfunction.

“the eat cat saw the red dog”

Nonsense mutation:

A new stop translation codon formed before the naturally occurring one.

Translation is stopped prematurely and a shortened protein is made

“the fat cat saw”

Frameshift mutation:

A deletion or insertion of one base results in a change in the translational reading frame

“the efa tca tsa wth ere ddo”

Question 18

Know what is polyploidy, and the types of polyploidy

Answer 18

Polyploidy, the condition in which a normally diploid cell or organism acquires one or more additional sets of chromosomes. In other words, the polyploid cell or organism has three or more times the haploid chromosome number.

More than diploid number of cells

Triplody (69), tetraploidy (92)

10% of miscarriages, incompatible with life

Question 19

Know what is aneuploidy and types; know the disorders covered in lecture

Answer 19

Aneuploidy: 1 or 3 copies of a single chromosome

Monosomy - Turner syndrome (a female is born with 1 “X” chromosome)

Polysomy -

Trisomy

Down Syndrome: Extra chromosome on the 21st (Trisomy)

Edwards Syndrome: Extra chromosome on 18th (Trisomy)

Klinefelter Syndrome: XXY - male is born with an extra copy of the X chromosome

XYY Syndrome - may have increased risk of learning difficulties and speech development

XXX Syndrome - Learning difficulties, decreased muscle tone, seizures, or kidney problems

Question 20

Know what it is meant by “Multifactorial Disorders;” know what Teratogenesis/teratogens means; know when are teratogens most affected

Answer 20

Multifactorial Disorders: Both multiple genes and the environment could affect one trait

Teratogenesis is literally birth defects.

the process by which congenital malformations are produced in an embryo or fetus.

IMPORTANT :

• Gross malformations (What you can see with yo eyes)
• Cleft Lip
• Club foot
• Hydrocephalus
• Neurobehavioral and metabolic anomalies (Stuff you can’t see)
• Teratogens most affected

Development occurs in three stages:
-Conception through week 2

-Embryonic period: Weeks 3 through 8
Gross malformations produced by teratogens
- Fetal period: Week 9 through delivery
Functions disrupted with teratogen exposure

Question 21

Know what it is meant by “Mitochondrial Disorders.”

Answer 21

Mitochondria are unable to completely metabolize/generate energy

Loss of muscle coordination, muscle weakness

Gastrointestinal disorders, severe constipation

Developmental delays, learning disabilities

Visual and/or hearing problems

Neurological problems, seizures

Heart, liver, or kidney disease

Increased risk of infection

Respiratory disorders

Thyroid dysfunction

Poor growth

Diabetes

Dementia

Question 22

Know, in general terms, genetic tech covered in lecture

Answer 22

DNA fingerprinting:

Used to test parentage and used in forensics

DNA sequencing:

Dideoxynucleotides (ddNTPs) lack the 3’-hydroxyl group necessary for forming a phosphodiester bond

Recombinant DNA:

E.g. Insulin

Not just bacterium, but other species, as well

Issues:

Did it go to the right place?

Rodents epigenetics are not as complicated as humans are making it harder to clone

CRISPR: Clustered regularly interspaced short palindromic repeats

Bacterial defense system

repeating sequences of genetic code, interrupted by “spacer” sequences

Remnants of genetic code from past invaders

Serves as a genetic memory that helps the cell detect/destroy invaders

Cut by Cas9 protein

Very precise and cheap

RNA sequencing : epigenetics

Prenatal screening:

You may go into preterm labor

Now you can get blood tests done

BBB is not kept 100% separate, high false positive rate