Genes and Genetic Diseases Flashcards
Information covering the various topics of the "Genes and Genetic Diseases" lecture.
The study of biologic heredity
Genetics
The basic unit of heredity
Gene
The field of genetics concerned with the structural and functional studies of the genome
Genomics
DNA representing all of the genes for a given species
Genome
Name the 3 basic parts of Nucleotide
- Deoxyribose (pentose sugar)
- Phosphate molecule
- Nitrogenous base
Nucleotide nitrogenous bases can be broken down into 2 basic groups
- Purines
2. Pyrimidines
Name the Purines associated with DNA
- Adenine
2. Guanine
Name the Pyrimidines associated with DNA
- Cytosine
2. Thymine
How does complementary pairing occur (general)?
A Purine binds with Pyrimidine:
- A to T
- C to G
The basic building block of Proteins
Amino Acids
The number of Amino Acids associated with human physiology
20
Nucleic Acid which contains the transcribed instructions for protein synthesis
Messenger RNA (mRNA)
Site of Transcription
Nucleus
Nucleic Acid which provides the machinery needed for protein synthesis
Ribosomal RNA (rRNA)
Nucleic Acid which delivers Amino Acids to the Ribosome
Transfer RNA (tRNA)
Site of Translation
Cytoplasm
T/F: DNA never leaves the nucleus
TRUE
4 ways in which mRNA is process
- Removing some parts (Introns)
- Keeping some parts (Extrons, “expressed”)
- Adding some bases
- Cutting and Splicing mRNA
_____ acts as a pattern/template telling the cell how to line up Amino Acids for Protein synthesis
mRNA
Cellular structure that holds mRNA and binds Amino Acids during Protein synthesis
Ribosome
Process which involves taking the instructions transcribed from DNA to mRNA and using them for Protein synthesis
Translation
_____ refers to 3 consecutive bases on mRNA
Codon
_____ refers to 3 consecutive bases on tRNA that are complementary to an mRNA Codon
Anticodon
Substance that directs the creation of all Proteins and cell
DNA
Sequences of DNA which contain the instructions for making a Protein
Gene
Chromosomes that are Sex-linked
X and Y chromosomes
T/F: The X chromosome is Dominant
FALSE
_____ refers to all chromosomes other than sex-linked
Autosomal
Human cells containing 46 chromosomes (23 pairs); Diploid cells
Somatic Cells
Human cells containing 23 chromosomes; Haploid cells
Gametes
The process which forms Haploid cells from Diploid cells
Meiosis
Chromosome Structure:
Notated as “p”
Short arm
Chromosome Structure:
Notated as “q”
Long arm
Chromosome Structure:
The region of attachment between sister chromatids
Centromere
Chromosome Structure:
End “caps” containing multiple base pairs which shorten with each cell division
Telomere
A Chromosome pair that are virtually identical are said to be _____
Homologous
Example of a Nonhomologous pair of Chromosomes
XY
Any inherited alteration of genetic material
Mutation
The 2 basic types of Mutation
- Chromosome aberrations
2. Base pair substitutions
Choose: Somatic Cells or Gametes
Mutations in this type of cell can be transmitted to offspring
Gametes
An agent known to increase the frequency of mutations
Mutagen
The 2 basic types of Mutagens
- Radiation
2. Chemicals
The 4 basic types of Base Pair Substitution Mutations
- Silent
- Missense
- Nonsense
- Frameshift
A DNA sequence change that does not change the Amino Acid sequence of the Gene
Silent Mutation
A type of Mutation that results in a single Amino Acid change in the translated Gene
Missense Mutation
A type of Mutation in which an mRNA [STOP] Codon is either produced or removed
Nonsense Mutation
An alteration of DNA in which an addition or deletion of a Base Pair occurs
Frameshift Mutation
Examples of consequences of Mutation which result in a gain of function
(Associated with Dominant Disorders)
- Production of new Protein product
- Overexpression of a Protein product
Examples of consequences of Mutation which result in a loss of function
(Associated with Recessive Disorders)
Loss of 50% Protein product
May or may not be adequate for normal function.
A Mutation that occurs in absence of exposure to known Mutagens
Spontaneous Mutation
Areas of the Chromosomes that have high Mutation rates
Mutational Hotspots
Example of a Mutational Hotspot in Humans
Cytosine base followed by a Guanine base
A specific position of a Gene along a Chromosome
Locus
A different form of a particular Gene at a given Locus
Allele
A Locus that has two or more Alleles that occur with appreciable frequency
Polymorphism
The genetic makeup of an organism
Genotype
The observable, detectable, or outward appearance of the Genetics of an organism
Phenotype
When all copies of a Gene/Loci (between Chromosomes) are alike, they are said to be _____
Homozygous
When all copies of a Gene/Loci (between Chromosomes) are different, they are said to be _____
Heterozygous
When only one copy of a Gene exists, it is said to be _____
Hemizygous
In studying Pedigrees, the person with whom the disorder begins is referred to as the _____
Proband
Process of turning a Gene “ON”
Promoted by external influence.
Induction
Process of turning a Gene “OFF”
Repression
The ability of a Gene to express its function
Penetrance
When many Genes can affect one Trait
Polygenic
When both multiple Genes and the environment can affect one Trait
Multifactorial
When one Gene can mask the effect of another
Epistasis
When one Gene might depend on another Gene
Complementary
When two Genes together might create a new Phenotype
Collaborative
The probability that parents of a child with a genetic disease will have yet another child with the same disease
Recurrence Risk
When one parent is affected by an Autosomal Dominant disease and the other is normal, the occurrence and recurrence risks for each child are _____
50%
When inheriting a dominant mutant gene fails to be expressed, the trait is said to have _____
Reduced Penetrance
Disorders that can be expressed differently among individuals are said to have _____
Variable Expressivity
The percentage of individuals with a specific Genotype who also express the expected Phenotype
Penetrance
The variation in a Phenotype associated with a particular Genotype
Expressivity
Disorder type that is manifested only when both members of the gene pair (Homozygous) are affected
Autosomal Recessive Disorders
The mating of two related individuals
Consanguinity
X chromosome or Y chromosome:
Location of most Sex-linked Disorders
X chromosome
Presence in one individual of two or more cell lines characterized by distinctive karyotypes
Mosaicism
A change in chromosome number
Aneuploidy
The presence of only one member of a chromosome pair
Severe; often causes abortion.
Monosomy
The presence of more than 2 chromosomes to a set
Polysomy
The presence of three chromosomes to a set
Trisomy
Most common trisomy disorder (and most common chromosome disorder)
Down Syndrome (Trisomy 21)
The normal separation of chromosomes during cell division
Disjunction
The failure of homologous chromosomes or sister chromatids to separate normally during Mitosis or Meiosis
Nondisjunction
Type of Chromosome Aberration that usually the cause of Aneuploidy
Nondisjunction
Autosomal Aneuploidy in which only an extra portion of a chromosome is present
Partial Trisomy
Trisomies occurring only in some cells of the body
Chromosome Mosaics
The best known example of Aneuploidy
Down Syndrome (Trisomy 21)
Aneuploidy whose signs/symptoms include:
- Mental retardation
- Low nasal bridge
- Epicanthal folds
- Protruding tongue
- Poor muscle tone
Down Syndrome (Trisomy 21)
T/F: The risk of offspring with Trisomy 21 increases with maternal age
TRUE
Aneuploidy resulting in a female that is XXX
Trisomy X
Aneuploidy termed “Metafemales”
Trisomy X
Autosomal Aneuploidy or Sex-linked Aneuploidy:
Down Syndrome (Trisomy 21)
Autosomal Aneuploidy
Aneuploidy whose signs/symptoms (variable) include:
- Sterility
- Menstrual irregularity
- Mental retardation
Trisomy X (“Metafemales”)
Aneuploidy resulting in a female with that is X_
Turner Syndrome
Aneuploidy whose signs/symptoms include:
- Sterility (absence of ovaries)
- Short stature
- Webbing of the neck
- Edema
- Underdeveloped breasts and wide nipples
- High number of aborted fetuses
Turner Syndrome
Aneuploidy resulting in an individual with at least 2 X chromosomes and 1 Y chromosome
Klinefelter Syndrome
Increase or Decrease:
Generally, in Aneuploidy disorders, additional X chromosomes will _____ abnormalities.
Increase
Aneuploidy whose signs/symptoms include:
- Male appearance
- Development of female-like breasts
- Small testes
- Sparse body hair
- Long limbs
Klinefelter Syndrome
3 Agents of Chromosomal Breakage
- Ionizing Radiation
- Chemicals
- Viruses
5 Types of Chromosomal Damage involving Breakage and Rearrangement
- Deletion
- Inversion
- Isochromosome Formation
- Ring Formation
- Translocation
Chromosomal Breakage and Rearrangement:
Disorder resulting from the deletion of a short arm of Chromosome 5
Cri du Chat Syndrome
Chromosomal Breakage and Rearrangement:
The presence of a repeated gene or gene sequence
Duplication
Chromosomal Breakage and Rearrangement:
Duplication in the same region as _____ causes mental retardation but no physical abnormalities
Cri du Chat Syndrome
Chromosomal Breakage and Rearrangement:
Reversal of gene order; usually occurring from a breakage that is reversed during reattachment
Inversion
Chromosomal Breakage and Rearrangement:
2 Types of Inversion
- Pericentric
2. Paracentric
Chromosomal Breakage and Rearrangement:
Inversion resulting in genes moved to the opposite side of the Centromere
Pericentric Inversion
Chromosomal Breakage and Rearrangement:
Inversion involving a break on the same arm of the chromosome
Paracentric Inversion
The interchanging of material between nonhomologous chromosomes
Translocations
A Translocation at the point of the Centromere
Robertsonian Translocation
Areas on chromosomes that develop distinctive breaks or gaps when cells are cultured
Fragile Sites
Disorder involving a weakened site on the long arm of the X chromosome
Fragile X Syndrome
The second most common cause of mental retardation
Fragile X Syndrome
Disorder in which a small region of a sex chromosome gene undergoes repeated duplication, resulting in a longer gene which is susceptible to methylation
Fragile X Syndrome
Many genes act together to influence an expressed trait
Multifactorial Inheritance
When expression of a disease existed in two related family members
Concordance
When expression of a disease exists in on family member but not a second
Discordance
An environmental agent that produces abnormalities during embryonic or fetal development
Teratogenic Agent
3 Types of Teratogenic Agents
- Radiation
- Chemicals and Drugs
- Infectious Agents
- Folic acid Deficiency
Why is Mitochondrial DNA subject to mutations at a higher rate than Nuclear DNA?
Lack of repair mechanisms
Where does all of an offspring’s Mitochondrial DNA come from?
The Mother
Mitochondrial DNA codes for the proteins needed for _____
Aerobic Metabolism