Unit 2 Flashcards
What is the sequence from DNA to Protein?
Replication, transcription, and translation
What is DNA replication?
DNA is separated (unzipped) and two new strands are formed using each previous strand to create 2 exact copies
What is transcription?
DNA to RNA; mRNA
What is translation?
RNA to a protein; tRNA
Define retrovirus
Viruses that use RNA as their genetic material and carry code for enzyme reverse transcriptase; converts RNA to DNA
Define gene polymorphism
Change in the sequence of DNA which then results in a change in the sequence of mRNA
What is a silent mutation?
A mutation that doesn’t change the primary protein sequence
Define Mutations
Any inherited alteration of genetic material; noticeable changes in the organism
What is an example of a favorable mutation?
Sickle Cell Anemia in Africa; protects against malaria
List the 3 types
Point mutations, frameshift mutations, and base-pair substitution
What is a point mutation?
A mutation that doesn’t change the reading frame; change only one single base
Can point mutations be silent?
Yes they don’t always change the protein sequence; silent mutation
What happens when the protein sequence is changed in a point mutation?
Missense mutation or nonsense mutation
What is a missense mutation?
Changing of one base changes one amino acid to another
What is nonsense mutation?
Changing of one base changes the codon from an amino acid to a stop codon resulting in a short protein
What is a frameshift mutation?
Insert or delete one or more base pairs in the reading frame shifting everything
Can frameshift mutations be silent?
No
What is a base-pair substitution?
One base pair is replaced by another
Can a base-pair substation be silent?
Yes if the substitution does not change the amino acid; silent substitution
What is a mutagen?
Agents that are known to increase the frequency of mutations
Give some examples of mutagens
Ionizing radiation, chemical agents, UV radiation, viruses
What is a mutational hot spot?
Some regions of the DNA that are weak and often mutated
What is a karyotype?
An ordered display of chromosomes from largest to smallest; best done during metaphase of Mitosis
Define homologous chromosomes
Nearly identical chromosomes; the same number 5 and 5
Define non-homologous chromosomes
Non-identical chromosomes; different number 9 and 22
How can we detect chromosomal abnormalities in the fetus?
Amniocentesis and Chorionic villus sampling
Define euploid
Cells that have a multiple of the normal number set (23) chromosomes; 23 x ____
Define haploid
One set of 23 chromosomes (sex cell)
Define diploid
Two sets of 23 chromosomes; 46 total (somatic cell)
Define polyploid
When a euploid has more than the diploid number of chromosomes; still contain a multiple of 23 chromosomes
Define triploid
Three sets of 23 chromosomes; 69 total - fetus will not survive
Define tetraploid
Four sets of 23 chromosomes; 92 total - fetus will not survive
Define aneuploidy
Cell that does not contain an exact multiple of 23 chromosomes; 45 or 47 total
Define trisomy
Cell containing three copies of one of the chromosome “pairs”; 47 total
Define monosomy
Presence of only one of any of the chromosomes “pairs”; 45 total
What is disjunction?
The process of splitting chromosomes into equal amounts of genetic material to each gamete
What is nondisjunction?
An error in which homologous chromosomes or sister chromatids fail to separate normally during meiosis or mitosis; gives rise to aneuploidy
Give an example of autosomal aneuploidy
Down Syndrome (trisomy 21)
Name characteristics of Down Syndrome
Low nasal bridge, round face, long and flat tongue, low set ears, short stature, heart defects, and respiratory defects
Give examples of sex aneuploidy
Turner’s Syndrome (monosomy X), Triplo-X (trisomy XXX), and Klinefelter’s Syndrome (trisomy XXY)
Name characteristics of Turner’s syndrome
Sterile, short, webbed neck, widely spaced nipples, little body hair, and underdeveloped breasts
Name characteristics of Triplo-X
Sterile, menstrual irregularity, and mental retardation (gets worse with more X’s)
Name characteristics of Klinefelter’s syndrome
Male appearance, female-like breasts, small testes, sparse body hair, and long limbs (gets worse with more X’s)
List chromosomal structure abnormalities
Breakage, deletions, inversions, duplications, and translocations
Define chromosomal breakage
If a chromosome breaks, physiological mechanisms will usually repair it; breaks can heal in a way that alters the structure of the chromosome
What is a clastogen?
Agents of chromosomes breakage
Give some examples of clastogens
Ionizing radiation, chemicals, and certain viruses
Define deletions
A breakage resulting in loss of DNA
Give an example of a deletion
Cri du chat (cry of the cat)
What is Cri du chat?
Deletion of short arm (p) of chromosome 5
Name characteristics of Cri du chat
Low birth weight, mental retardation, microcephaly (small head), and shrieking cry
Define inversions
Breakage followed by a reversal of the fragment during re-insertion (putting piece in backwards)
Define duplications
Replication of a gene sequence resulting in an amino acid sequence being repeated multiple times
What happens if duplication occurs in the same region as Cri du chat?
Mental retardation occurs, but no physical abnormalities
Define translocation
Interchange of material between non-homologous chromosomes (13-4, 2-5); from one place to another
When does translocation occur?
When two chromosomes break and the segments are rejoined in an abnormal arrangement
Define gene
Segment of DNA that codes for a protein or regulatory molecule
Define locus
The physical (geographic) location of a gene along a chromosome
Define allele
Different form (copy) of a particular gene
Define homozygous
Two alleles of a particular gene on a pair of homologous chromosomes are identical
Define heterozygous
Two alleles of a particular gene on a pair of homologous chromosomes are not identical
Define genotype
Genetic make-up of an organism; what they have
Define phenotype
Visible observation or tested for; what they show
Define carrier
can pass “bad” gene to their offspring but are not affected themselves
Define proband
The first in the family to be seen in a health care facility and diagnosed with the disease
What is recurrence risk?
The probability (%) of a family with a specific genotype having a child with an expected phenotype
Define penetrance
The proportion of individuals of a particular genotype that expresses its phenotype in a specific environment; how many people with the disease actually show it