Unit 2 Part 2: Non-Mendelian Genetics Flashcards
Responsible for the traits that Mendel studied in pea plants were on different chromosomes.
Genes
T/F: When genes are close to each other on the same chromosome, they usually segregate at random during meiosis and therefore their expression does not support Mendel’s predictions.
F; do not segregate
Genes close on a chromosome are packaged into the same gametes and are said to be ______
linked
Refers to the transmission of genes on the same chromosome
Linkage
Who identified more than 50 genes on Drosophila’s 4 pairs of chromosomes?
Thomas Morgan
Do not assort independently and do not produce Mendelian ratios for crosses tracking two or more genes
Linked Genes
He discovered that many seemed to be linked together. They are almost always inherited together & only rarely become separated.
Thomas Morgan
Grouped genes into 4 linkage groups
Thomas Morgan
Linkage maps were first developed by?
Alfred Sturtevant
A map based on the frequencies of combination between markers during crossover of homologous chromosome
Linkage Map
A map of the genes on chromosome based on linkage analysis
Linkage Mapping
T/F: A linkage map does not show the physical distances between genes but rather their relative position, as determined by how Gene loci are inherited together.
T
Some DNA sequences are nearly always inherited together, like two inseparable friends. This nonrandom association between DNA sequences is called
Linkage Disequilibrium (LD)
The human genome consists of many LD blocks, where stretches of alleles stick together, interspersed with areas where crossing over is prevalent. LD blocks, called __________, could be used to track genes in populations.
haplotypes
Is a combination of alleles at multiple linked loci that are transmitted together
Haplotype
May refer to as few as 2 loci or to an entire chromosome depending on the number of recombination events that occurred between a given set of loci
Haplotype
The term haplotype is a portmantaeu of ________
Haploid Genotype
Is a set of single nucleotide polymorphisms (SNPs) on a single chromatid that are statistically associated
Haplotype
T/F: Sex is determined by genetic information in human
T
It extensively controls physical, psychological, and behavioral traits which are also influenced by genetic information
Sex-Linked Traits
may be categorized by how sex affects phenotypic traits, including sex itself as a trait (i.e., sex determination), sex-linked trait, sex-limited trait, and sex- influenced trait
Sex-related genetics
Genes on the Y chromosome
Y-linked
Genes on the X chromosome
X-linked
T/F: Y-linked traits are rare because the chromosome has few genes, and many of its genes have counterparts on the X chromosome.
T
T/F: X-linked traits are passed from male to male, because a female does not have a X chromosome.
F; Y-linked traits are passed from male to male, because a female does not have a Y chromosome.
T/F: No other Y-linked traits besides infertility (which obviously can’t be passed on) are yet clearly defined.
T
T/F: Some traits at first attributed to the Y chromosome are actually due to genes that have been inserted into that chromosome from other chromosomes, such as a deafness gene.
T
Part of Chromosome
Mutation = Infertility
SRY
Part of Chromosome
Controlled by multiple genes
Tooth Enamel Formation
Part of Chromosome
Mutation = Male can produce necessary fluids but no sperm; angospermia
AZF / Azoospermia Factor
Part of Chromosome
Pseudoautosomal regions - create homology between X & Y chromosomes
PAR2
T/F: A disproportionate number of X-linked genes cause illness when mutant. The chromosome includes 4 percent of all the genes in the human genome, but accounts for about 10 percent of Mendelian (single-gene) diseases.
T
T/F: X-linked diseases are more common in males
T
T/F: In males, X-linked traits are passed just like autosomal traits—that is, two copies are required for expression of a recessive allele and one copy for a dominant allele.
F; females
T/F: In males, however, a single copy of an X-linked allele causes expression of the trait or illness because there is no copy of the gene on a second X chromosome to mask the effect. A man inherits an X-linked trait only from his mother.
T
The human male is considered __________ for X-linked traits, because he has only one set of X- linked genes.
hemizygous
X-Linked Recessive or X-Linked Dominant
Always expressed in the male
X-Linked Recessive
X-Linked Recessive or X-Linked Dominant
Affected male inherits trait from heterozygote or homozygote
X-Linked Recessive
X-Linked Recessive or X-Linked Dominant
Affected female inherits trait from the affected father and affected or heterozygote mother
X-Linked Recessive
X-Linked Recessive or X-Linked Dominant
Expressed in a female homozygote and very rarely in a female heterozygote
X-Linked Recessive
X-Linked Recessive or X-Linked Dominant
Expressed in females in one copy
X-Linked Dominant
X-Linked Recessive or X-Linked Dominant
Much more severe effects in males
X-Linked Dominant
X-Linked Recessive or X-Linked Dominant
High rates of miscarriage due to early lethality in males
X-Linked Dominant
X-Linked Recessive or X-Linked Dominant
Passed from male to all daughters but to no sons
X-Linked Dominant
The X-linked recessive trait, the blood- clotting disease hemophilia B is also known as
Christmas disease and factor IX (“FIX”) deficiency
A rare neurodevelopmental disorder. Less lethal than HD
Rett Syndrome
T/F: In X-linked dominant inheritance, if male is affected, daughter will always affected
T
A ________ affects a structure or function of the body that is
present in only males or only females. The gene for such a trait may be ________.
Sex-limited trait , autosomal
Typical child with this syndrome cannot speak, use her hands, walk, eat or breathe easily
Rett Syndrome
Are due to genes on autosomes, and the expression of these traits are limited so that normally only one sex is affected.
Sex-limited traits
Although an inherited disease that causes symptoms associated with pregnancy is obviously sex-limited, the male genome may play a role by contributing to the development of supportive structures, such as the ________
Placenta
A sudden rise in blood pressure late in pregnancy
Preeclampsia
T/F: If a man’s first wife had preeclampsia, his second wife had double the risk of developing it
T
are autosomal traits that are influenced by sex. If a male has one recessive allele, he will show that trait, but it will take two recessive for the female to show that same trait. One such gene is baldness.
Sex-influenced traits
Traits that may be expressed in both sexes but occurs more frequently in one sex
Sex-influenced traits
T/F: Single genes seldom completely control a phenotype in the way that Mendel’s experiments with peas suggested.
T
A genotype (allele combination) that causes death
Lethal Allele Combinations
Tay-Sachs disease is lethal by age of
3 or 4
Causes death before the individual can reproduce, which prevents passage of mutations to the next generation.
Lethal Genotype
T/F: Achondroplastic Dwarfism is an autosomal dominant trait, but is most often the result of a spontaneous (new) mutation.
T
A lethal genotype in humans is _______________, which has the distinct phenotype of a long trunk, short limbs, and a large head bearing a flat face.
Achondroplastic Dwarfism
Type of relationship between alleles, with a heterozygote phenotype intermediate between the two homozygote phenotypes
Incomplete Dominance
When F1 generation (all pink flowers) is self pollinated, the F2 generation is 1:2:1
red, pink, white
Incomplete Dominance
T/F: Enzyme deficiencies in which a threshold level is necessary for health illustrate incomplete dominance only.
F; both complete and incomplete dominance
Is an example of incomplete dominance that can be observed in carriers on both the molecular and whole-body levels
Familial hypercholesterolemia (FH)
Different alleles that are both expressed in a heterozygote are codominant.
Co-dominance
The ABO blood group system is based on the expression of __________ ______.
Codominant Alleles
A single-gene disease with many symptoms, or a gene that controls several functions or has more than one effect
Pleiotropy
Both alleles are simultaneously expressed in the heterozygote
Codominant Traits
It refers to interaction between different genes, not between the alleles of the same gene
Epistasis
A gene that affects expression of another
Modifier Gene
A familiar epistatic interaction is ________, in which one gene blocks the action of genes that confer color.
albinism
Bombay Phenotype
Epistasis
It results from an interaction between a gene called H and the I gene that confers ABO blood type. The H gene controls the placement of a molecule to which antigens A and B attach on red blood cell surfaces.
Bombay Phenotype
Bombay was named by
Dr. Bhande
T/F: Individual with Bombay phenotype can receive blood only from Bombay blood group people
T
The most common form of this autosomal dominant condition is a defect in an elastic connective tissue protein called fibrillin. The protein is abundant in the lens of the eye, in the aorta (the largest artery in the body, leading from the heart), and in bones of the limbs, fingers, and ribs.
Marfan syndrome (Pleiotropy)
It can occur when genes encode enzymes or other proteins that are part of the same biochemical pathway, or when proteins affect the same body part
Genetic Heterogeneity
osteogenesis imperfecta
Genetic Heterogeneity
An environmentally caused trait that appears to be inherited
Phenocopy
Such a trait can either produce symptoms that resemble those of a known single-gene disease or mimic inheritance patterns by affecting certain relatives.
Phenocopy
The limb birth defect caused by the drug ________ is a phenocopy of the rare inherited illness phocomelia.
thalidomide
A birth defect caused by exposure to a widely used teratogen was more likely than a sudden increase in incidence of a rare inherited disease.
Phocomelia (Phenocopy)
Regulate organ development
Homeotic genes
Code for transcription factors
Homeobox genes
Determine the identities of each body segment
Hox genes
Refers to the percentage of individuals who have a particular genotype who have the associated phenotype
Penetrance
Refers to variability in severity of a phenotype, or the extent to which the gene is expressed
Expressivity
T/F: Complete penetrance is rare.
T
Refers to the inheritance of a trait governed by more than one genes. Generally, three or more genes govern the inheritance of polygenic traits. Multiple independent genes have an additive or similar effect on a single quantitative trait.
Polygenic Traits
Type 2 diabetes mellitus
Polygenic Disorder
A polygenic disorder with multiple genes located on different chromosomes contributing to its susceptibility.
Type 2 diabetes mellitus
