Exam 1- Genes And Genetic Disease Flashcards
Codon
Sequence of 3 nitrogenous bases that specifies a particular amino acid. Triplets of based.
Sequence of 3 nitrogenous bases that specifies a particular amino acid. Triplets of based.
Codon
Noncoding segment spliced out of mRNA
Intron
Segment of mRNA that codes for proteins
Exon
Alteration of DNA capable of being passed to offspring.
Missense _________
Nonsense _________
Frameshift _________
Mutation
Substance that alters genetic material (DNA)
Mutagen
Segment of DNA that is the basic unit of inheritance
Gene
Strand of condensed chromatin visible right before cell division. A somatic cell has 23 pairs of_______________. 1 sex_______________ and 22 nonsectarian_____________(autosomes)
Chromosome
Chromosome that is not a sex chromosome. 1 pair of sex chromosomes and 22 pairs of___________.
Autosome
Different version of a paired gene at a given locus.
If 2____________ are found together, the___________ that is observable is the dominant, and the one whose effects are hidden is recessive.
Dominant_____________: capital letter
Recessive: lowercase letter
Can be codominant
Ex: Hgb A vs Hgb S
Allele
A DNA mutation that involves an addition or deletion of a number of base pairs that is not a multiple of three, and thus alters all of the codons downstream from the site of insertion or deletion.
Frameshift mutation
Interchanging of genetic material between nonhomologous chromosome. One chromosome breaks and becomes part of another chromosome.
Type of chromosomal aberration/ alteration.
Ex: Philadelphia chromosomal____________. Increased chances of CML and ALL.
Translocation
Loci on a pair of chromosomes have identical genes (type O)
Homozygous
DD, dd affected or unaffected homozygous
A pair of chromosomes have different genes (Person/Type A and B genes mix and are different), that, when mixed are called this.
Dd affected or unaffected____________.
Heterozygous
One of the chromosomes in somatic cell has only one copy instead of 2 normal.
Monosomy
One of the chromosomes in somatic cell has 3 copies instead of the normal 2.
Trisomy
The genetic material
Genotype
Expression of genes
Phenotype
Diploid cell makes a copy of itself
Mitosis
The process by which haploid cells are formed from diploid
Meiosis
1) RNA polymerase binds to DNA promoter region
2) transcription
3) mRNA is spliced to remove noncoding sections
4) mRNA leaves the nucleus
5) translation
Steps of protein synthesis
Ex: Turner syndrome, Down syndrome, fragile X syndrome, klinfelter syndrome
Chromosomal disorder
A somatic cell that has 46 chromosomes in its nucleus
Diploid cell
Determined by one gene mutation. Autosomal dominant, autosomal recessive, or X-linked recessive.
Strongly determined by genes.
Ex: CF, hemophilia A, sickle cell
Single gene disorder
Disorder linked to X Chromosome
Y chromosome only carries a few genes, so most sex-linked traits are X-linked.
More often seen in males than female, because they only have 1 X chromosome.
Dominant (rare) or recessive.
X-linked disorders
Cells have 3 copies of each chromosome
Triploidy
Inactivated X chromosome that is seen in normal female cells.
Barr body
Has 23 chromosomes, one member of each pair. Will meet up with another _________ to make a diploid. Aka gamete.
Haploid cell
More sets of chromosomes. In multiples of 23. Incompatible with life. More than 2 copies of each chromosome.
Triploidy- 3 sets of 23 chromosomes
Tetraploidy- 4 sets (92 chromosomes)
Polyploidy
Error during meiosis or mitosis. Homologous chromosomes fail to separate normally. Results in aneuploidy.
Nondisjunction
_____________ have Rr so can still pass it on but don’t have the expressed trait.
Phenotypically normal. Carries disease causing alleles.
Have to have 2 recessive genes to have expressed trait (rr).
Carrier
XY- male
XX- female
1 pair of sex chromosomes and 22 of autosomes.
Sex chromosomes
Abnormal number of single chromosomes. Loss of chromosome (monosomy) material more serious than duplicate.
23 pairs usually. On one pair you’re missing one chromosome and only have 1 (monosomy). On another pair you have 2 from one parent, for a total of 3 instead of 2 (trisomy). Autosomal aneuploidy usually lethal, but Can survive with trisomy13, 18, and 21.
Sex chromosomal aneuploidy is not lethal (except for monosomy (X): Y chromosome has little genetic info and extra X chromosome is usually inactive (fragile X). Having 1 X is lethal.
Aneuploidy
3 copies of the 21st chromosome.
Nondisjunction in egg.
Linked with maternal age.
Intellectual disability, poor muscle tone, increases congenital heart defects, increased risk for Alzheimer’s after age 40.
Down Syndrome (Trisomy 21)
Broken chromosomes or loss in DNA in 1 chromosome can have serious effect.
Cri du chat Syndrome- deletion of long arm of chromosome 5. Microcephalic, low birth weight.
Chromosomal deletion
Multiple copies of DNA portion. Less serious than deletion. But when they have offspring, chromosomes don’t align and offspring can have issues.
Chromosomal duplication
Single-gene disorders
Diseases are rare. Very rare for two affected people with the dominant trait to produce offspring. Dd if they have one capital D, they are effected. Only need to inherit a D from 1 affected parent to get the disease.
Genotype of affected person: DD or Dd
Genotype of unaffected person: dd
Males and female equally likely.
One of the patents has to have the disease.
Heterozygous individuals pass it on to 50% of their offspring. Does not skip generations because there are no carriers.
75% chance to pass on (recurrence rate) if both parents Dd (affected):
25% DD homozygous affected
50% Dd heterozygous affected
25% dd homozygous unaffected
Phenotype: observable effect
Ex: achondroplasia, Huntingtons
Autosomal dominant disorders
Single gene disorder
Disease: A person must have 2 recessive alleles. Must receive a a recessive gene from each parent. (dd) to get the disease. non sex-linked (same in M and F).
Rare, but number of carriers can be high.
Usually in children not parents.
If both parents heterozygous carriers (Dd) 25% of passing it on (recurrence rate). 50% that offspring will be phenotypically normal and 25% genetically normal.
Example: CF
Chances increase with consanguineous mating between relatives.
Autosomal Recessive trait (d)
Sections of chromosome. Each_______ is responsible for different characteristics of a person. If same on both ________ in a chromosome pair, it’s homozygous. If different, heterozygous.
Locus
Variation in a phenotype linked to a particular genotype. Severity may vary. A parent with a mild expression of a disease (they may not even know that they have it) can transmit the gene to a child, who can the exhibit severe expression of the disease.
Ex: neurofibtomytosis
Expressivity
Female with 3 X chromosomes.
Sterility, menstrual irregularity, to mental retardation.
Worse with each additional X.
Trisomy on the X chromosome.
Trisomy X
Chromosomal disorder.
At least 2 Xs and 1 Y.
Male appearance, develop breasts, small testes, sparse body hair, long limbs.
Klinefelter Syndrome
Areas on chromosomes that develop distinctive breaks or gaps when cells are cultured. No apparent relationship to disease.
Chromosome fragile sites
Chromosomal disorder
Site on long arm of the X chromosome.
Usually in men because only one X.
Associated with mental retardation, second in occurrence to Down Syndrome.
Fragile X Syndrome
Liability distribution. For multifactorial traits, as the number of multifactorial traits increases, the liability for that disease increases as well. As the factors reach the threshold, the person will definitely be effected.
Though liability may be the same between men and women, the threshold may be different.
Threshold model
Complete set of chromosomes in an individual
Karyotype
_______________ of a trait is the percentage of the individuals with a specific genotype who also express the expected phenotype. Incomplete means that the person with the disease-causing allele may not exhibit the disease phenotype ally all, even though it might be transmitted to the next generation.
Penetrance
Affected fathers (XhY) will transmit the affected genes to all his daughters but not his sons (he gives his sons the Y gene).
Affected mothers (XhXh) will pass to all her sons and all her daughters will be carriers.
Carrier mothers (XhXH) will pass the condition to 50% of their sons (no 2nd X to counteract disease gene) and 50% of her daughters will be carriers.
X-linked recessive disorders
Rare
Affected father will pass the condition on to daughters but not sons
Affected mother will pass on to 50% of children (50% of getting c chromosome from mom), both male and female
X-linked dominant disorders
2 of the same identical traits. In females, we have XX sex traits, a homologous pair. Males have a nonhomolygous pair.
Homologous
Intron
Noncoding segment spliced out of mRNA
Exon
Segment of mRNA that codes for proteins
Mutation
Alteration of DNA capable of being passed to offspring.
Missense mutation
Nonsense mutation
Frameshift mutation
Mutagen
Substance that alters genetic material (DNA)
Gene
Segment of DNA that is the basic unit of inheritance
Chromosome
Strand of condensed chromatin visible right before cell division. A somatic cell has 23 pairs of chromosomes. 1 sex chromosomes and 22 nonsectarian chromosomes (autosomes)
Autosome
Chromosome that is not a sex chromosome. 1 pair of sex chromosomes and 22 pairs of autosomes.
Allele
Different version of a paired gene at a given locus.
If 2 alleles are found together, the allele that is observable is the dominant, and the one whose effects are hidden is recessive.
Dominant allele: capital letter
Recessive: lowercase letter
Can be codominant
Ex: Hgb A vs Hgb S
Frameshift mutation
A DNA mutation that involves an addition or deletion of a number of base pairs that is not a multiple of three, and thus alters all of the codons downstream from the site of insertion or deletion.
Translocation
Interchanging of genetic material between nonhomologous chromosome. One chromosome breaks and becomes part of another chromosome.
Type of chromosomal aberration/ alteration.
Ex: Philadelphia chromosomal translocation. Increased chances of CML and ALL.
Homozygous
Loci on a pair of chromosomes have identical genes (type O)
DD, dd affected or unaffected homozygous
Heterozygous
Loci of a pair of chromosomes have different genes (Type Dd)
Dd affected or unaffected heterozygous.
Monosomy
One of the chromosomes in somatic cell has only one copy instead of 2 normal.
Trisomy
One of the chromosomes in somatic cell has 3 copies instead of the normal 2.
Genotype
The genetic material
Phenotype
Expression of genes
Mitosis
Diploid cell makes a copy of itself
Meiosis
The process by which haploid cells are formed from diploid
Steps of protein synthesis
1) RNA polymerase binds to DNA promoter region
2) transcription
3) mRNA is spliced to remove noncoding sections
4) mRNA leaves the nucleus
5) translation
Chromosomal disorders
Ex: Turner syndrome, Down syndrome, fragile X syndrome, klinfelter syndrome
Diploid cell
A somatic cell that has 46 chromosomes in its nucleus
Single gene disorder
Determined by one gene mutation. Autosomal dominant, autosomal recessive, or X-linked recessive.
Strongly determined by genes.
Ex: CF, hemophilia A, sickle cell
X-linked disorders
Disorder linked to X Chromosome
Y chromosome only carries a few genes, so most sex-linked traits are X-linked.
More often seen in males than female, because they only have 1 X chromosome.
Dominant (rare) or recessive.
Triploidy
Cells have 3 copies of each chromosome
Barr body
Inactivated X chromosome that is seen in normal female cells.
Haploid cell
Has 23 chromosomes, one member of each pair. Will meet up with another haploid to make a diploid. Aka gamete.
Polyploidy
More sets of chromosomes. In multiples of 23. Incompatible with life. More than 2 copies of each chromosome.
Triploidy- 3 sets of 23 chromosomes
Tetraploidy- 4 sets (92 chromosomes)
Nondisjunction
Error during meiosis or mitosis. Homologous chromosomes fail to separate normally. Results in aneuploidy.
Carrier
Carriers have Rr so can still pass it on but don’t have the expressed trait.
Phenotypically normal. Carries disease causing alleles.
Have to have 2 recessive genes to have expressed trait (rr).
Sex chromosomes
XY- male
XX- female
1 pair of sex chromosomes and 22 of autosomes.
Aneuploidy
Abnormal number of single chromosomes. Loss of chromosome (monosomy) material more serious than duplicate.
23 pairs usually. On one pair you’re missing one chromosome and only have 1 (monosomy). On another pair you have 2 from one parent, for a total of 3 instead of 2 (trisomy). Autosomal aneuploidy usually lethal, but Can survive with trisomy13, 18, and 21.
Sex chromosomal aneuploidy is not lethal (except for monosomy (X): Y chromosome has little genetic info and extra X chromosome is usually inactive (fragile X). Having 1 X is lethal.
Down Syndrome (Trisomy 21)
3 copies of the 21st chromosome.
Nondisjunction in egg.
Linked with maternal age.
Intellectual disability, poor muscle tone, increases congenital heart defects, increased risk for Alzheimer’s after age 40.
Chromosomal deletion
Broken chromosomes or loss in DNA in 1 chromosome can have serious effect.
Cri du chat Syndrome- deletion of long arm of chromosome 5. Microcephalic, low birth weight.
Chromosomal duplication
Multiple copies of DNA portion. Less serious than deletion. But when they have offspring, chromosomes don’t align and offspring can have issues.
Autosomal dominant disorders
Single-gene disorders
Diseases are rare. Very rare for two affected people with the dominant trait to produce offspring. Dd if they have one capital D, they are affected. Only need to inherit a D from 1 affected parent to get the disease.
Genotype of affected person: DD or Dd
Genotype of unaffected person: dd
Males and female equally likely.
One of the parents has to have the disease.
Heterozygous individuals pass it on to 50% of their offspring. Does not skip generations because there are no carriers.
75% chance to pass on (recurrence rate) if both parents Dd (affected):
25% DD homozygous affected
50% Dd heterozygous affected
25% dd homozygous unaffected
Phenotype: observable effect
Ex: achondroplasia, Huntingtons
Autosomal Recessive trait (dd)
Single gene disorder
Disease: A person must have 2 recessive alleles. Must receive a recessive gene from each parent. (dd) to get the disease. non sex-linked (same in M and F).
Rare, but number of carriers can be high.
Usually in children not parents.
If both parents heterozygous carriers (Dd) 25% of passing it on (recurrence rate). 50% that offspring will be phenotypically normal and 25% genetically normal.
Example: CF
Chances increase with consanguineous mating between relatives.
Locus
Sections of chromosome. Each locus is responsible for different characteristics of a person. If same on both locus in a chromosome pair, it’s homozygous. If different, heterozygous.
Expressivity
Variation in a phenotype linked to a particular genotype. Severity may vary. A parent with a mild expression of a disease (they may not even know that they have it) can transmit the gene to a child, who can the exhibit severe expression of the disease.
Ex: neurofibtomytosis
Trisomy X
Female with 3 X chromosomes.
Sterility, menstrual irregularity, to mental retardation.
Worse with each additional X.
Trisomy on the X chromosome.
Klinefelter Syndrome
Chromosomal disorder.
At least 2 Xs and 1 Y.
Male appearance, develop breasts, small testes, sparse body hair, long limbs.
Chromosome fragile sites
Areas on chromosomes that develop distinctive breaks or gaps when cells are cultured. No apparent relationship to disease.
Fragile X Syndrome
Chromosomal disorder
Site on long arm of the X chromosome.
Usually in men because only one X.
Associated with mental retardation, second in occurrence to Down Syndrome.
Threshold model
Liability distribution. For multifactorial traits, as the number of multifactorial traits increases, the liability for that disease increases as well. As the factors reach the threshold, the person will definitely be effected.
Though liability may be the same between men and women, the threshold may be different.
Karyotype
Complete set of chromosomes in an individual
Penetrance
Penetrance of a trait is the percentage of the individuals with a specific genotype who also express the expected phenotype. Incomplete means that the person with the disease-causing allele may not exhibit the disease phenotype allele at all, even though it might be transmitted to the next generation.
X-linked recessive disorders
Affected fathers (XhY) will transmit the affected genes to all his daughters but not his sons (he gives his sons the Y gene).
Affected mothers (XhXh) will pass to all her sons and all her daughters will be carriers.
Carrier mothers (XhXH) will pass the condition to 50% of their sons (no 2nd X to counteract disease gene) and 50% of her daughters will be carriers.
X-linked dominant disorders
Rare
Affected father will pass the condition on to daughters but not sons
Affected mother will pass on to 50% of children (50% of getting c chromosome from mom), both male and female
Homologous
2 of the same identical traits. In females, we have XX sex traits, a homologous pair. Males have a nonhomolygous pair.
