Chapter 2 for Exam 1 Patho

genes

, the basic units of inheritance, are composed of sequences of deoxyribonucleic
acid (DNA) and are located on chromosomes.

nucleotides, each subunit of DNA

one deoxyribose, a phosphate molecule, and one of four types of nitrogenous bases.

single ringed pyrimidines

cytosine and thymidine

double ringed purines

adenine and guanine

DNA is

a double helix with the two strands connected by the nitrogenous bases, with thymine always
bonding to adenine, and guanine always bonding to cytosine

Base pairs that make ip the genetic code in DNA and contribute to protein synthesis

adenine (A) with Thymine (T) or Uracil in (RNA) and cytosine (C) with guanine (G)

codons

triplet sets of nitrogenous bases in specific orders, that code for specific
amino acids. Remember that several __ correspond to the same amino acid in many cases.

how many amino acids are there in DNA

20

DNA replication happens in the

nucleus

DNA replication is

untwisting and unzipping of the DNA strand, is based on complementary base pairing, in which a single strand of DNA serves as the template for attracting complementary bases that form a new strand of DNA.

DNA polymerase

is the primary enzyme involved in replication, adds bases to the new DNA strand and preforms “proofreading” functions

Mutation

is an alteration of genetic material

Missense mutations

change amino acid codes

nonsense mutations

produce stop codons before needed

frameshift mutation

substances that cause mutations

transcription

is the process by which messenger RNA is synthesized in the nucleus from DNA template and is an enzyme in RNA polymerase

what is the difference between RNA and DNA

one is single stranded and the other is double, and one has jus ribose sugar molecule instead of deoxyribose and one has uracil rather than thymine

Gene splicing

remove introns and those remain spliced together exons before mRNA migrated to the cytoplasm

Introns

intervening and are not expressed

exons

are expressed within gene

Translation

s the process by which RNA directs the synthesis of polypeptides, takes place in the
ribosomes, which consist of proteins and ribosomal RNA (rRNA).

what happens during translation

mRNA interacts with transfer RNA (tRNA), a molecule that has an attachment site for
a specific amino acid and an anticodon. The ribosome moves along the mRNA, matching different tRNAs to codons on the mRNA, and forming a growing chain of amino acids called a polypeptide.

anticodon

a region that matches up with a 3-base codon on the mRNA.

example of nonsense mutations

UAA, UAG or UGA

Somatic cells

contain 46 chromosomes (23 pairs), are called Diploid cells and are formed through mitosis

Gametes

contain 23 chromosomes, are haploid cells, one member of each chromosome pair and is formed through meiosis. sperm and egg

humans have how many pairs of chromosome and what do they entail

23 pairs, with 22 of them are autosomes and is seen in females and males.

women

XX sex chromosome

male

XY sex chromosome

karyogram

is an ordered display of chromosomes arranged according to length and the location of the
centromere. visual representation os the individuals chromosomes type.

Euploid

ells have the normal number of chromosomes (either diploid or haplod)

Polyploidy

is a condition in which a cell has some multiple of the normal number of chromosomes.

Triploidy

three copies of each chromosome are lethal

tetraploidy

four copies of each chromosome are lethal

Aneuploidy

is when a cell does not have a multiple of 23 chromosomes: there is an extra or missing single
chromosome.

Nondisjunction

Failure of homologous chromosomes or sister chromatids to separate normally during
meiosis or mitosis, resulting in aneuploidy

Trisomy

a type of aneuploidy in which one chromosome is present in three copies.

Partial trisomy

is one in which only part of a chromosome is present in three copies.

Monosomy

is a type of aneuploidy in which one chromosome is present in only one copy. In general,
these cause more severe physical defects than do trisomies, i.e., loss of chromosome material has more severe consequences than the duplication of chromosome material

Down syndrome

a trisomy of chromosome 21, affects 1 in 800 to 1 in 1000 live births

Turner syndrome

45, X karyotype

Klinefelter syndrome

47, XXY karyotype

Triple X syndrome

47, XXX karyotype

Jacobs syndrome

47,XYY karyotype

Cri du chat syndrome

deletion of short arm of chromosome 5, reacts to low brith weight, severe intellectual suability , microcephaly (small brain), odd teeth and ears.

Fragile X syndrome

second most common cause of intellectual disability after Down syndrome, higher in males because they only have one X chromosome.

Locus

position of a gene along a chromosome

Allele

different forms of genes located at the same locus on a chromosome.

Polymorphism

locus has two or more alleles that occur with appreciable frequency, ex: have both tall and short

Homozygous

allele are identical for locus

Heterozygous

alleles are different for a locus

genotype

genetic makeup

phenotype

the outward appearance of the genetics of an organism

dominant gene

gene is observable and makes others

recessive

gene that is hidden, and can only be expressive if there is two copies of small gene

PKU genotype - phenylketonuria

genetic defiency of enzyme that breaks down the amino acid phenylanine usually in sodas

autosomal dominant

affected offspring sally produced by union of normal parent with affect heterozygous parent

example of autosomal dominant

Huntington disease, dwarfism and polydactyly (multiple fingers and toes).

autosomal recessive

both parents of affected individuals are heterozygous carries

example of autosomal recessive

cystic fibrosis

X-linked recessive modes of inheritance

genetic conditions cased by mutations on sex chromosomes. If a male inherits a recessive disease gene on the X chromosome, he will be affected by the disease because the Y chromosome does not carry a normal allele to counteract the effects. more often in males that females because men only have one X when women have two. however, males cannot pass it onto sons since they give their Y to their sons and not their X. skipped generations.

Huntingtons disease

autosomal dominant, affects males and females are equally likely and the two sexes are equally likely to transmit to their offspring. Affected heterozygous individuals transmit the trait to approximately half their children. delayed form seen after 40 years of age

crossing over

occurs during mitosis 1, can cause recombination of alleles located not he same chromosome.

Multifactorial Inheritance Traits

That result from the combined effects of several loci are polygenic. When environmental factors also influence the trait, it is_. have a threshold of liability. Once the threshold of liability has been crossed, the disease may be expressed

penetrance

of a trait is the percentage of individuals with a specific genotype who also exhibit the expected phenotype. A gene that is not always expressed phenotypically is said to have incomplete penetrance, e..g, retinoblastoma

Expressivity

is the extent of variation in phenotype associated with a particular genotype. If the expressivity of a disease is variable, penetrance may be complete but the severity of the disease can vary greatly, e.g., neurofibromatosis type 1 - phenotypes may vary from mild café au lait spots to far more severe profiles

Epigenetics

same DNA sequence can produce different phenotypes due to chemical modification that
alters expression of genes. It involves changes, such as the methylation of DNA bases, that do not alter the DNA sequence but can alter the expression of genes.

Genomic imprinting

which is associated with gene methylation, results in differing expression of a disease
gene, depending on which parent transmitted the gene. One parent imprints (inactivates) the gene during transmission to offspring.

an example of genetic imprinting

Prader-Willi vs Angelman syndrome due to deletion on chromosome 15. If paternally inherited: Prader-Willi Syndrome- short stature, obesity, hypogonadism, If deletion is maternally inherited

Angolan Syndrome

intellectual disability, seizures, ataxia

Autosomal recessive inheritance affects

males and females in equal proportions

Consanguinity

(mating of related individuals) is sometimes present in families with autosomal recessive
diseases, and it becomes more prevalent with rarer recessive diseases. The disease may be seen in siblings but not their parents

In each normal female somatic cell

one of the two X chromosomes is inactivated early in embryonic development, giving rise to a Barr body. X inactivation is random, fixed, and incomplete (i.e., only part of the chromosome is actually inactivated) and involves methylation.

Gender is determined embryonically by

the presence of the SRY gene on the Y chromosome. Embryos that have a Y chromosome (and thus the SRY gene) normally become males, whereas those lacking the Y chromosome become females