1.2.1 - Mendelian Genetics Flashcards
It is the branch of biology that deals with heredity and variation of organisms.
Genetics
It carries the hereditary information or the genes of an individual
Chromosomes
It is a type of chromosome that contain DNA that codes for the same genes
- they are alike but not exactly the same
Homologous chromosomes
These are exact replicas of each other
Sister chromatids
- it is a unit of heredity
- a section of DNA sequence encoding a single protein
Gene
It is the entire set of genes in an organism
- 1st to 23rd pair
Genome
These are two genes that occupy the same position on homologous chromosomes
-it covers the same trait
- ‘flavors’ of a trait
Alleles
It is a fixed location on a strand of DNA where a gene or one of its alleles is located
Locus
It is the genetic makeup of an organisms
- e.g. Tt, tt, Xx
Genotype
- It is the physical appearance of an organism
- Genotype + environment
Phenotype
It is having identical genes (one from each parent) for a particular characteristic
- TT, tt
Homozygous
It is having two different genes for a particular characteristic
- Tt
Heterozygous
It is a trait in which a gene is carried on a sex chromosome
Sex-linked trait
These are traits controlled by genes on one of 22 pairs of autosomes (non-sexual chromosomes)
Autosomal traits
- It is the allele of a gene that masks or suppresses the expression of an alternate allele
- the trait appears in the heterozygous condition
Dominant
- It is an allele that is masked by a dominant allele
- does not appear in the heterozygous condition, only in homozygous.
Recessive
- a genetic cross involving a single pair of genes (one trait)
- parents differ by a single trait
Monohybrid cross
- a genetic cross between two different genes that differ in two observed traits
Dihybrid cross
What represents the Parental generation
“P”
- What represents the First filial generation
- offspring from a genetic cross
F1
What represents the second filial generation of a genetic cross
F2
- It is the phenotype that is the most common expression of a particular allele combination in a population.
- It may be recessive or dominant
Wild type phenotype
This phenotype is a variant of a gene’s
expression that arises when the gene undergoes a change, or mutation
Mutant phenotype
It is an illness that typically begins in early adulthood, causing uncontrollable movements and changes in behavior and thinking (cognition)
Huntington disease
Huntington Disease is an ________
Autosomal Dominant
It is a kind of disease that each child of an affected individual need inherit only one copy of the mutant gene to develop the disease
An example of this is the Huntington Disease
Autosomal Dominant
10% of people who have Huntington Disease are under the age of 20 y/o and acquired what we call ________
Juvenile Huntington Disease
- This type of inherited disease affects each child independently
- It affects every generation and both sexes (wala syang inii-spare)
Classic Autosomal Dominant Inheritance
True or False
The single-gene disease is distinctive with penetrance
- since all cells harbor the mutation, if the person has inherited it
penetrance = predictive ability
True
Another distinction of the single-gene disease is that mutations stay in certain populations because some tend to have children with people similar to themselves or their relative. This is what we call _______
Consanguinity (incest haha)
Sickle cell disease and Muscular dystrophy are examples of what type of disease?
Single-gene disease
This test is consisting of sick children and their parents which can reveal whether the child inherited two disease-causing mutations from carrier parents, or whether a dominant mutation arose anew
Tests of Trios
It is a term used when an individual has a dominant mutation that arose anew
- did not inherit it from anyone
de novo
It is the theory where traits of two parents “blend” together and inherited by the offsprin
Blending Theory of Inheritance
What experiment counteracted the blending theory?
Mendel’s experiment with peas
Why are peas ideal for probing heredity?
- easy to grow
- develops quickly
- traits that take one of two easily distinguishable forms
- Inheritance that involves the passing of discrete units of inheritance, or genes, from parents to offspring
- It is Mendel’s theory
- aka the gene Idea
Particulate Theory of Inheritance
Medel was the first to discover that traits were passed on ______
intact
What theory is this?
- Genes are present within chromosomes inside the cell
- Genes and chromosomes are in
pairs in diploid cells
Chromosome Theory of Inheritance
Who proposed and proved the Chromosome Theory of Inheritance?
- proposed by Walter Sutton
- proved by Thomas Morgan
Patterns of Inheritance | What principle is this?
- one allele masks another
- one allele was dominant over the other in the F1 generation
Principle of Dominance
Patterns of Inheritance | What principle is this?
When gametes are formed, the pairs of hereditary factors (genes) become separated, so that each sex cell (egg/sperm) receives only one kind of gene
Principle of Segregation
Patterns of Inheritance | What principle is this?
Genes located on different chromosomes will be inherited independently of each other
Principle of Independent Assortment
According to Mendel, short plants were ________ , while tall plants were _______
Short plants: True breeding
Tall plants: Non-true breeding
Some dominantly inherited diseases are said to be due to a ________ because they result from the action of an abnormal protein that interferes with the function of the normal protein
gain-of-function
Huntington disease results from ________ in which the dominant mutant allele encodes an abnormally long
protein that prevents the normal protein from functioning in certain brain cells.
- The protein encoded by the mutant HD allele must be abnormal, not absent, to cause the disease
gain-of-function
What is the extra protein in the Huntington disease that causes a gain-of-function?
Huntingtin protein
A single gene on chromosome ________, confers eye color by controlling melanin synthesis.
- If this gene is missing, albinism results, causing pale skin and red eyes
- recessive allele of this gene confers blue color and a dominant allele confers brown
Chromosome 15, OCA2
Near the OCA2 gene on chromosome 15 is a second gene, ________, that controls expression of the OCA2 gene
- recessive allele of this gene abolishes the control over OCA2, and blue eyes result
HERC2
A person must inherit two copies of the ____________ to have blue eyes.
recessive allele in HERC2
A heterozygous individual is also a ________
carrier
True or False
Carriers can develop a life-threatening breakdown of muscle if exposed to the combination of environmental heat, intense physical activity, and dehydration
Case for sickle cell disease
True
sicke cell trait
True or False
Most genes have more than two alleles and more than two variations of the associated trait.
True
An individual with two different recessive alleles for the same gene is termed as _______
Compound Heterozygote
It is a variant that occurs when a child has a recessive allele from each parent w the variant located at a different position with the same gene
Compound Heterozygous Variant
How is nucleotide inheritance determined?
- Laboratory-based: 10x Genomics or fosmid pool-based strategy
- Computer-based: SHAPEIT2, Eagle2, HapCUT2
This disease may present in juvenile or adult onset forms, which is a result of the compound heterozygosity between two alleles, one that causes the classic infantile disease in homozygotes and another that allows some residual HEXA enzyme activity
Yay-Sachs disease
- It was the first genetic disorder for which mass post-natal genetic screening was available
- It is a rare inherited disorder that causes an amino acid called phenylalanine to build up in the body
Phenylketonuria
It is an inherited form of sickle cell disease that affects red blood cells both in the production of abnormal hemoglobin, as well as the decreased synthesis of beta globin chain
Sickle cell-beta thalassemia
A recessive trait is sis to arise from a _______ because recessive allele usually prevents the production or activity of the normal protein
Loss-of-function
Recessive diseases tend to be more severe, and produce symptoms earlier, than dominant diseases
True
The half normal amount of the enzyme that a carrier produces is usually sufficient to maintain health. The one normal allele, therefore, compensates for the mutant one, to which it is dominant.
True
Most autosomal recessive conditions appear unexpectedly in families, because they are transmitted silently, through ______
heterozygotes (carriers)
In what situation can autosomal recessive condition be more likely to recur?
Blood relatives have children together — Consanguinity (“shared blood”)
Identify whether it is Autosomal Dominant or Autosomal Recessive or both
Makes and females are affected with equal frequency
Both
Identify whether it is Autosomal Dominant or Autosomal Recessive or both
Successive generations affected until no one inherits the mutation
Autosomal Dominant
Identify whether it is Autosomal Dominant or Autosomal Recessive or both
Affected individual has an affected parent, unless he/she has a de novo mutation
Autosomal Dominant
Identify whether it is Autosomal Dominant or Autosomal Recessive or both
It can skip generations
Autosomal recessive
Identify whether it is Autosomal Dominant or Autosomal Recessive or both
Affected individual has parents who are affected (both) or are carriers (at least one)
Autosomal recessive
This law reflects the actions of chromosomes and the genes they carry during meiosis
Two Factors:
- equal allele distribution into gametes
- random combinations of gametes
Law of Segregation (Mendel’s 1st Law)
- This law states that for two genes on different chromosomes, the inheritance of one gene does not influence the chance of inheriting the other gene
- The two genes are packaged into gametes at random
Law of Independent Assortment (Mendel’s 2nd Law)
- It is a useful tool to do genetic crosses
- Looks like a windowpane
- Used to determine the probability of outcome of offspring
Punnett square
- It is a lethal genetic disease affecting Caucasians
- It is caused by a mutant recessive gene carried by 1 in 20 people of European descent
- It affects transportin tissues – mucus is accumulated in lungs, causing infections.
Cystic Fibrosis
- It is a fatal genetic disorder that causes the progressive breakdown of nerve cells in the brain
- aka quintessential family disease because every child of a parent with HD has a 50/50 chance of inheriting the faulty gene
- it’s allele is dominant
Huntington Disease
It is a mating that involve parents that differ in two genes (two independent traits)
Dihybrid cross
What is the common phenotypic ratio for a dihybrid cross?
9:3:31
- You do this test when you have an individual with an unknown genotype
- It is a cross with a homozygous recessive individual
Test cross
