GENETICS AND INHERITANCE Flashcards
This involves the transmission of genetic material from parents to offspring, ensuring the continuity of genetic traits across generations
Inheritance
This refers to an organism’s ability to survive and reproduce in its environment, thereby passing on its genes to the next generation
Biological fitness
Study of genes and their transmission from one generation to the next
Genetics
DNA sequences that contain instructions for building proteins
Genes
They are located at specific
positions on chromosomes and occur in pairs, with one inherited from each parent.
Genes
Represent the complete set of
genetic material present in an organism, encompassing all of its DNA, including both coding and non-coding regions.
Genomes
Involve the comprehensive
examination of an individual’s genetic material to gather valuable information
Genome Wide Arrays (GWA)
Information from the GWA
Ethnicity, possible illness, tolerance, deficiency
Structures within the nucleus,
composed of DNA and protein
Chromosomes
First 22 pairs of chromosomes
Autosomes
Last 1 pair of chromosomes
Allosome
The composite visual display of all of the chromosomes of an individual
Karyotype
These are specific and alternative versions of the same gene pair, occupying the same locus on homologous chromosomes
Alleles
Refer to chromosome pairs that are similar in size, shape, and banding patter, with one member of each pair inherited from each parent. While they resemble each other, they are not identical and may carry different alleles of particular genes
Homologous
Two identical alleles at a particular locus
Homozygous
Two different alleles at a particular locus
Heterozygous
Masks or suppresses the expression of its complementary allele.
Always expressed, even if heterozygous.
Are not always more common than recessive one; sometimes they may be rare in a population
Dominant Allele
Will not be expressed if paired with a dominant allele (heterozygous). Will only be expressed if individual is homozygous for the recessive allele
Recessive allele
An individual’s complete set of alleles
→ The complete genetic material of an organism along with its
noncoding nucleic acid sequence
→ Determines the genetic makeup of an organism.
→ Consists of all the genes inherited from both parents.
→ Determines the potential range of phenotypic traits an organism can express.
Genotype
→ Worked with pea plants in the 1850s in Austria
→ Did multiple genetic experiments to
develop basic rules of inheritance
Gregor Mendel
→ Gametes carry only one allele of each gene
→ One is from dad and one is from mom
→ explains that during gamete
formation, alleles for each gene segregate, ensuring that each gamete carries only one allele for each gene.
→This process allows for genetic variation and ensures that offspring inherit a combination of alleles from both parents, contributing to genetic diversity.
Law of Segregation
→ states that genes for different traits
are inherited independently of each other during gamete formation, as long as they are located on different chromosomes.
→ This principle holds true during meiosis, where genes for separate traits assort into gametes without regard to the inheritance of other genes. However, this law applies only if the genes in question are located on different chromosomes, allowing for the random assortment of alleles during gamete formation. This process allows for the independent distribution of alleles for different traits, resulting in a wide variety of genetic combinations in offspring.
Law of independent assortment
→ a process during which
homologous chromosomes exchange genetic material, further increases genetic diversity by shuffling alleles between chromosomes.
→ Without this, each chromosome would contain genes inherited solely from either the mother or the father, resulting in less genetic variation among offspring.
Crossing over
in the presence of a dominant
allele, its corresponding trait will be expressed. This principle applies to genetic inheritance, where one allele may mask the expression of another allele.
Law of Dominance
Dominant allele completely masks the recessive allele, resulting in the expression of the dominant trait
Complete dominance
traits blend together, producing an intermediate phenotype
Incomplete dominance
→ Both alleles are expressed
independently, without blending, resulting in the simultaneous presence of both traits.
→ This allows for the expression of multiple traits without the dominance of one over the other.
Co-dominance
→ “Many genes”
→ refers to the inheritance of traits
that are determined by the interaction of multiple genes. These traits are not solely influenced by the genes inherited from one’s parents but rather by the combined effects of many genes working together.
polygenic traits
→ These are two genes that are closely situated on the same chromosome. They are physically adjacent, often overlapping, indicating that during genetic recombination processes such as crossing over, they are unlikely to separate. This suggests that certain alleles remain together even when crossing over occurs.
→ physically located on the same chromosome
→ May be inherited together
→ Maybe”shuffled”during crossing
over during meiosis
Linked allele
→ These refer to genetic traits or conditions that are specifically associated with the sex chromosomes, namely the X and Y chromosomes in humans.
→ These traits or conditions are influenced by the sex of the individual, as they are located on the sex chromosomes.
Sex-linked chromosome
○ 23d pair of chromosomes
○ Not homologous
○ X and Y chromosomes carry different genes
Sex chromosome
Have one X and one Y chromosome
Male
Have two X chromosomes
Females
→ The sex doesn’t matter. Both males
and females are affected.
→ Refers to a pattern of inheritance
where individuals must inherit two copies of the recessive allele to express the trait
→ This may skip generations, as carriers may not exhibit symptoms but can pass the allele to the offspring
Autosomal recessive
→ occurs during cell division,
particularly during meiosis, where chromosomes or chromatids fail to separate properly.
→ It is either Monosomy or Trisomy
Non-disjunction
→ Trisomy21
→ is one of the most prevalent
chromosomal disorders. It is caused by the presence of an extra copy of chromosome 21, resulting in a total of 47 chromosomes instead of the typical 46.
→ Itisautosomal.Ithasdifferent symptoms: it may be mental, physical, and cognitive
Down syndrome (47, 21+)
→ This is a genetic condition characterized by the presence of an extra X chromosome in males, resulting in a karyotype of 47, XXY.
→ It is a sex-linked condition occurring on chromosome 23. It affects males, indicated by the presence of the Y chromosome. This syndrome impacts the endocrine system, which governs hormones, thus influencing physical, mental, and cognitive health. Individuals with this often experience significant hormonal imbalances, contributing to various health challenges.
The symptoms often lean towards
qualities that are more biologically
feminine
Klinefelter’s Syndrome (47, XXY)
→ The sex doesn’t matter. Both males
and females are affected.
→ Refers to a pattern of inheritance
where the presence of a single copy of the dominant allele on one of the autosomal chromosomes is sufficient to express the trait.
→ It appears in every generation of an affected family and affected individuals.
Autosomal dominant
→ is characterized by the presence of
an extra Y chromosome in males, resulting in a karyotype of 47, XYY. While some symptoms may overlap with Klinefelter syndrome, such as hormonal imbalances, it is generally less severe. Both conditions involve abnormalities in chromosome 23, but their specific manifestations
Jacob Syndrome (47, XYY)
→ Monosomy
→ This is sex-linked. The sex of this is female.
→ all or part of one X chromosome is absent
→ Affects the endocrine system severely
Turner syndrome (45, XO)
→ Piece of a chromosome breaks off
→ We can easily detect this with karyotype.
Deletion
→ Deletion of chromosome 5
→ usually found in the crying of
babies, is characterized by a distinct high-pitched cry resembling that of a cat.
→ severe developmental delay and cognitive deficits and distinctive facial abnormalities
Cri du chat syndrome
→ Piece of chromosome breaks off and re-attaches to a different chromosome
→ Change of location, a process similar to crossing over but is intended to occur only during meiosis. If translocation occurs outside of meiosis, it can result in a genetic disorder.
Translocations
Everyone is affected without skipping generations. This means that at least one individual in every generation carries or expresses the trait, even if not all members of the generation have it.
Dominant
It may skip generations but can be carried and potentially expressed in future offspring.
Recessive
People with PKU cannot convert the amino acid Phenylalanine to _____ due to a mutation in the gene that codes for PAH.
Tyrosine
→ is a metabolic disease that is
caused by a buildup of Phenylalanine in the body due to an enzyme deficiency, particularly the hepatic enzyme Phenylalanine Hydroxylase (PAH).
Phenylketonuria (PKU)
PKU is a metabolic disease that is
caused by a buildup of ______ in the body due to an enzyme deficiency, particularly the hepatic enzyme Phenylalanine Hydroxylase (PAH).
Phenylalanine
Most commonly occurring in children, that results in progressive destruction of the nervous system caused by the absence of a vital enzyme called hexosaminidase-A (Hex-A).
Tay-sachs disease (TSD)
TSD the absence of the enzyme ____. Without this enzyme, fatty substances accumulate excessively in the brain, particularly in neurons and nerve cells. This accumulation is progressive and rapid because our brains shouldn’t have these fatty substances.
Hex-A
→ This is caused by
an inherited detect in a single gene (HTT). It is an autosomal dominant disorder, a person needs only one copy of the defective gene.
→ Isn’t expressed until mid-life
→ Each child of an affected individual has a 50% chance of inheriting the
lethal gene
Huntington’s disease
This means inherited on chromosome 1-22
Autosomal
This means inherited on either X or Y chromosome.
Sex-linked
PKU, Tay-Sachs, albinism
Autosomal recessive
Huntington’s Disease
Autosomal dominant
- this allele is found on only the X chromosome: can be in males or females)
★ e.g., color-blindness, hemophilia
X-linked recessive
- this allele is found on X chromosomes; can be in males or females)
★ e.g., hypophosphatemia
X-linked dominant
The allele is found on the Y chromosome and can only be in males.
Y-linked
→ Trait is rare in the pedigree
→ Trait often skips generations
(hidden in heterozygous carriers)
→ Trait affects males and females
equally
Autosomal recessive pedigree
→ Trait is rare in pedigree.
→ Trait skips generations
→ Males are more often affected than
females
→ Females are carriers
X-linked recessive pedigrees
→ Trait is common in pedigree
→ passed to ALL of their daughters
→ Males and females are equally likely to be affected
→ X-linked dominant diseases are extremely unusual
★ ex. incontinentia pigmenti (skin lesions)
X-linked dominant pedigrees
→ Traits on the Y chromosomeare
only found in males, never in
females.
→ The father’s traits are passed to
XY on all sons.
→ Dominance is irrelevant: there is
only 1 copy of each Y-linked gene
Y-linked gene
