Patho Neoplasms and Congenital

cyotsin and thymin

what are the pyrimidines

adenine and guanine

what are the purines

double helix untwists and unzips of dna strand

what is replication of dna

dna polymerase

what does complementary base pairing

frameshift mutation

insertion or deletion of one or more base pairs

causes a change in entire reading frame

what does a frame shift mutation cause

mutagens

agents known to increase frequency of mutation

radiation and chemicals

what are examples of mutagens

teratogens

cause damage during fetal development

exposure, timing, developmental stage

what do effects of teratogens depend on

Spontaneous mutation

occurs in absence of exposure to known mutagens

Mutational hot spots

areas of the chromosomes that have high mutation rates

- double stranded

- deoxyribose sugar

- uses thymine

- stays in nucleus

- stores instructions

describe dna

- single stranded

- ribose sugar

- uses uracil

- carries/uses instructions to make proteins

describe rna

dna stores instructions, rna carries instructions, ribosomes use instructions to make proteins

what is the path of dna, rna and ribosomes

transcriptions

DNA ---->. RNA

translation

RNA ------>. protein

⚬46 chromosomes (23 pairs)

⚬diploid cells

describe somatic cells

mitosis

what are somatic cells formed through

⚬contain 23 chromosomes

⚬haploid cells

describe gametes

meiosis

what are gametes formed through

Autosomes

the first 22 of the 23 pairs of chromosomes in males and females

Sex chromosomes

remaining pair of chromosomes

homologous pair (XX)

what are the chromosomes of females

nonhomologous pair (XY)

what are chromosomes of males

Haploid

One complete set (23)

Diploid

Two complete sets (46)

Triploidy (69)

Three complete sets

Tetraploidy

Four complete sets (92)

Polyploidy

having more than 46 chromosomes, with extra COMPLETE sets

Aneuploidy

an abnormal number of chromosomes

cell is missing or has an extra individual chromosome

describe Aneuploidy

3 copies of one chromosome (instead of 2) ---> Trisomy 21

what is trisomy

1 copy of one chromosome (instead of 2) ---> Turner syndrome

what is monosomy

Nondisjunction

chromosomes don't separate correctly leading to abnormal number of chromosomes

no separation ⟶ extra chromosome in one cell + missing chromosome in another

what does Nondisjunction result in

Partial trisomy

only part of the chromosome is present 3 times

Mosaicism

not all cells have the same chromosomes; "different pieces"

Down syndrome

most common autosomal aneuploidy (Trisomy 21)

with maternal age >35

what is increased risk of down syndrome

Sex Chromosome Aneuploidy

extra or missing X or Y chromosome

Y

which chromosome contains less genetic material

can be inactivated which reduces their effects

what can happen to extra X chromosomes

females

who does triple X affect

has 3x chromosomes

what is triple X

females

who does turner syndrome affect

has only 1x chromosome

what is turner syndrome

males

who does klinefelter syndrome affect

has 2x chromosomes + 1 Y

what is klinefelter syndrome

Down syndrome

intellectual disability, low nasal bridge, protruding tongue, low-set ears, poor muscle tone, congenitial heart defect

Turner syndrome

underdeveloped ovaries (sterile), short stature, webbing of neck, edema, wide nipples, underdeveloped breasts

Klinefelter syndrome

male appearance and develop female type breasts, small testes (usually sterile), sparse body hair, long limbs

Chromosome breakage

may or may not heal as "normal"

Deletions

broken or lost DNA; missing some genes

Cri du Chat syndrome "cry of the cat"

affected infants have high pitched cry, low birth weight, microcephaly, heart defects, intellectual disabilities

Duplications

repeated gene or gene sequence

Inversions

⚬2 breaks on a chromosome

⚬reversal of the gene order

position effect of inversions

gene moved ⟶ gene expression may change

Translocations

interchanging of material from one chromosome to another

Reciprocal translocation

exchange; 2 different chromosomes break and exchange pieces

Robertsonian translocation

2 chromosomes fuse together

13, 14, 15, 21, and 22

what chromosomes are involved with Robertsonian translocation

Fragile site

areas on chromosomes that develop distinctive breaks or gaps when cells are cultured

Fragile X syndrome

"fragile" area on long arm of the X chromosome

⚬intellectual disability

⚬Features: long face, prominent ears, crossed eyes

⚬higher incidence in males

what are characteristics of Fragile X syndrome

Locus

position of a gene on a chromosome

Allele

different version of a gene

•Homozygous = SAME (A+A or a+a)

•Heterozygous = DIFFERENT (A+a)

what is the difference between homozygous and heterozygous

Polymorphism

⚬gene location has multiple common versions in a population

Genotype

what genes they have

Phenotype

what they demonstrate; what you can see

•Dominant (A) - shows up

•Recessive (a) - can be hidden

what is dominant and recessive genes

⚬autosomal dominant

⚬autosomal recessive

⚬X-linked dominant

⚬X-linked recessive

what are modes of inheritance of single-gene diseases

Pedigree

a chart that summarizes family relationships, showing which members are affected by a genetic disease

Autosomal Dominant Inheritance

usually produced by union of normal parent with affected heterozygous parent

Recurrence risk

probability the individual will develop a genetic disease

Huntington disease

what is a autosomal dominant inheritance disease that has delayed age of onset

Penetrance

how many people with a particular genotype will actually show the trait

Expressivity

how severe or how strongly the trait appears

Epigenetics

modification alters the expression of genes

doesn't change the recipe, changes whether cell uses the recipe or ignores it

describe Epigenetics

Methylation

"mute" the gene

adding a methyl group to DNA

what happens in Methylation

Genomic imprinting

gene is turned off depending on which parent it came from ⟶ if both accidentally become active certain genes, will exhibit

Consanguinity

⚬mating of 2 related individuals

⚬dramatically increases recurrence risk of recessive disorders

cystic fibrosis

what is an example of an autosomal recessive inheritance

Sex-linked inheritance

caused by mutations on X or Y

X - usually affected in males

what chromosome is mostly affected by sex-linked inheritances

X Inactivation

one X chromosome in females permanently inactivated

Barr body

inactive X chromosome

Sex determination

SRY gene is on Y chromosome

testes

what does SRY gene is on Y chromosome trigger development of

x-linked recessive pedigrees

fathers cannot transmit to sons, can to all daughters

50%

sons of female carriers have ________ risk of being affected by x-linked recessive pedigrees

Duchenne Muscular dystrophy

what is an example of x-linked recessive inheritance

Sex-limited traits

occur in only one sex (i.e. inherited uterine or testicular defects)

Sex-influenced traits

occurring much more often in one sex than the other (i.e. male pattern baldness)

Multifactorial Inheritance

not every trait comes from ONE gene, some traits are influenced by many different genes working together

Polygenic trait

trait influenced by multiple genes

height, skin pigmentation

what are examples of polygenic traits