GENETICS REVIEWER IN DEPTALS

Incomplete dominance

A heterozygote (two different alleles present in the individual) shows the phenotype that is intermediate (blinding of the homozygous phenotype) between the two homozygous phenotypes. Neither allele is dominant over the other

Incomplete Dominance

Form of intermediate inheritance between two homozygous phenotypes.

● One allele is not completely dominant over the other allele.

● Results in a third phenotype from the combination of alleles from the parent.

Codominance

Another pattern of non-mendelian inheritance is co-dominance that results when one allele is not dominant over. The other the resulting heritage eye goat exhibit the traits of both parents

Law of Dominance

Gregor Mendel’s law states that when two alleles of an inherited pain are heterozygous, then, the allele that is expressed is dominant whereas the allele that is not expressed is recessive

Law of Segregation

Alleles segregate randomly into gametes: When gametes are formed, each allele of one parent segregates randomly into the gametes, such that half of the parent’s gametes carry each allele.

Law of Independent Assortment

Alleles of two (or more) different genes get sorted into gametes independently of one another.

NON-MENDELIAN TRAITS

Non-Mendelian inheritance is any pattern of inheritance in which traits do not segregate in accordance with Mendel’s laws.

INCOMPLETE DOMINANCE

Incomplete dominance is when a dominant allele, or form of a gene, does not completely mask the effects of a recessive allele, and the organism’s resulting physical appearance shows a blending of both alleles.

Codominance

Codominance occurs when two versions, or “alleles” of the same gene are present in a living thing, and both are expressed. Instead of one trait being dominant over the other, both traits appear. Ex: Camellia Flowers

Pedigree

Chart that shows the presence or absence of a trait within a family across generations.

Genotype

The genetic makeup of an organization (Ex. TT)

Phenotype

\- The physical characteristics of an organism. (ex. tall)

Dominant Allele

Allele that is phenotypically expressed over another allele.

Recessive Allele

Allele that is only expressed in absence of a dominant allele

Autosomal

Trait that is located on an autosome (non-sex chromosome)

Sex-linked trait

Trait that is located on one of the two sex chromosomes

Homozygous

Having two identical alleles for a particular gene.

Heterozygous

Having two different alleles for a particular gene.

Pedigrees

are used to analyze the pattern of inheritance of a particular trait throughout a family. Pedigrees show the presence or absence of a trait as it relates to the relationship among parents, offspring, and siblings. Pedigrees represent family members and relationships using standardized symbols.

Proband

First affected family member who seeks medical attention for a genetic disorder.

Autosomal Dominant Traits

Heterozygous and homozygous dominant individuals are affected.

Affected offspring have at least one affected parent.

Equal number of males and females.

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SEX RELATED INHERITANCE

It is a type of inheritance where the traits that the offspring will inherit depends on the sex that they will have.

x - chromosomes

present in all organisms

y - chromosomes

determines the possible sex of an organism

XY chromosome

male chromosome

XX chromosome

Female chromosome

SEX LIMITED TRAITS

are traits which are exclusively expressed in one sex of the species.

Traits are exclusive to one sex only

Lactation

\- is a trait that is exclusive to females. Only females are able to produce milk due to the presence of mammary glands and sex hormones for females.

Colorful feather tail of peacock

exclusive for male peacocks to show interest for peafowl (female).

Harelip

another term for cleft lip

Gout

\- having too much presence of uric acid in the body which is more common in males.

Pattern Baldness

hair situation which can be expressed in both sexes but more common in males

Sex-Influenced Traits

controlled by genes located in the body chromosomes

Sex-Linked Traits

controlled by genes located in the sex chromosomes

genetic linkage

When genes are on separate chromosomes, or very far apart on the same chromosomes, they assort independently. That is, when the genes go into gametes, the allele received for one gene doesn't affect the allele received for the other. In a double heterozygous organism (AaBb), this results in the formation of all 4 possible types of gametes with equal, or 25%, percent, frequency

Homologous chromosomes

Are paired chromosomes that carry the same genes, but may have different alleles of those genes. One member of each homologous pair comes from an organism's mom, the other from its dad.

Homologous Recombination

When genes are on the same chromosome but very far apart, they assort independently due to crossing over.

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This is a process that happens at the very beginning of meiosis, in which homologous chromosomes randomly exchange matching fragments. Crossing over can put new alleles together in combination on the same chromosome, causing them to go into the same gamete.

Linkage

\- tendency to "stick together" during meiosis

\- chromosomal maps based on recombination frequencies

\- can be used to find the relative positions of genes on a chromosome.

Parental Configurations Of Alleles

The ones that were already together on the chromosome in the organism before meiosis (i.e, on the chromosome it got from its parents).

Recombinant Configurations Of Alleles

\- Rare types of gametes contain this

\- Ones that can only form if a recombination event (crossover) occurs in between the genes.

Why are the recombinant gamete types rare?

The basic reason is that crossovers between two genes that are close together are not very common. Crossovers during meiosis happen at more or less random positions along the chromosome, so the frequency of crossovers between two genes depends on the distance between them. A very short distance is, effectively, a very small "target" for crossover events, meaning that few such events will take place (as compared to the number of events between two further-apart genes).

The Degree Of Genetic Linkage

can be used to construct genetic maps that show the relative positions of genes on a chromosome.

Recombination Frequency

\- Can be calculated by performing a genetic cross and analyzing the resulting offspring.

\- In a genetic cross involving two linked genes, the frequency of recombinant offspring can be used to calculate the recombination frequency. - The recombination frequency between two genes is equal to the number of recombinant offspring divided by the total number of offspring.

Gene mapping

is a procedure used to identify the locus.

Locus

refers to the position of the gene on the chromosome.

Linkage Mapping

determines the location of the gene in relation to other genes on the chromosome, but cannot determine the exact location of the gene.

Physical Mapping

is a more commonly used method to determine the exact location of a gene.

Thomas Hunt Morgan

found that genes controlling body color and wing type were on the same chromosome, but some process sometimes breaks the connection between these genes and allows for rearrangement of alleles

Alfred Sturtevant

one of Morgan's students - developed the notion of a genetic map to elucidate the specific loci of genes within a chromosome.

- reasoned that the farther apart two genes are, the more likely it is that crossing over will result in recombination.

Multifactorial Inheritance

Responsible for multifactorial traits

Empiric risk

Measures the likelihood that a trait will recur based on incidence

Incidence

Is the rate at which a certain event occurs

Enzymes

molecules that speed up chemical reactions

Helicase

(The unzipping enzyme) - an enzyme that unzips the double helix by breaking the hydrogen bonds between the complementary bases.

Primase

(the initializer) - an enzyme that synthesizes short RNA sequences called primers. These primers serve as a starting point for DNA synthesis

DNA Polymerase

(the builder) - An enzyme that replicates DNA to build a new strand.

Ligase

(The gluer) - an enzyme that connects two DNA strands together.

DNA Transcription

Coding region of DNA is converted to mRNA.

DNA Translation

Information based sequence of mRNA is used to dictate the amino acid sequence of the protein .

Gene expression

a process of controlling protein production genes turn on and off in response to their environments and the resulting needs of the cells.

Translational

the life expectancy of the mRNA varies and the longer it exists the more protein is produced. Also the more ribosomes attaching to the same strand of mRNA the faster the protein will be built

Post Translational

during this phase changes can be made to the polypeptide to make it functional so various enzymes attached to it and produce folding even different amino acids can be spliced out and ultimately that polypeptide chain that was produced if the mRNA becomes an active functional protein

MUTATIONS

\- Are changes made to an organism’s genetic material

\- Changes may be due to errors in replication, errors during transcription, radiation, viruses, and many other things.

POINT MUTATIONS

A large category of mutations that describe a change in single nucleotide of DNA, that causes that DNA to be different from the normal type gene sequence.

Insertion

\- Extra base pair is added to a sequence of bases - Example: Beta-Thalassemia - blood disorder that reduces the production of hemoglobin

Deletion

Extra base pair is deleted from a sequence. - Example: Cystic Fibrosis - hereditary disease that affects the lungs and digestive system; the body produces thick and sticky mucus that can clog the lungs and obstruct the pancreas

Substitution

\- Bases are swapped for different ones. - Example: Sickle Cell Anemia

GENETIC DISORDERS

\- Caused by an abnormality in the genetic makeup of an individual - Can be caused by chromosomal abnormality

Karyotype

\- An individual’s collection of chromosomes - Normal Human Karyotype: 46 chromosomes or 23 pairs - 22 pairs - autosomes (body chromosomes) - Last pair - would determine the gender (sex chromosomes) (Female: XX; Male: XY)

CRI-DU-CHAT SYNDROME

Also known as 5p-syndrome (5p minus syndrome) - A chromosomal condition that results when a piece of chromosome 5 is missing - Affected individuals have distinctive facial features, including widely set eyes (hypertelorism), low-set ears, a small jaw, and a rounded face.

DOWN SYNDROME

Trisomy 21 (trisomy means three copies, so three copies of chromosome 21 ang down syndrome) - Associated with intellectual disability, a characteristic facial appearance, and weak muscle tone (hypotonia) in infancy.

Microevolution

is a change in the frequency of gene variants, alleles, in a population, typically occurring over a relatively short time period.

Population Genetics

is the field of biology that studies allele frequencies in populations and how they change over time.

Gene Pool

consists of all the copies of all the genes in that population.

Allele (Gene) Frequency

refers to how common an allele is in a population. It is determined by counting how many times the allele appears in the population then dividing by the total number of copies of the gene.

Genotype Frequencies

the fraction of individuals with a given genotype.

Phenotype Frequencies

the fraction of individuals with a given phenotype.