gen bio 1

model system

system with convenient characteristics used to study a specific biological phenomenon to be applied to other systems

blending theory of inheritance

asserted that the original parental traits were lost or absorbed by blending in the offspring

theory of inheritence

a genetic framework explaining how traits are passed from parents to offspring, encompassing multiple models such as Mendelian inheritance and blending theory.

law of segregation

the principle that during gamete formation, the two alleles for a trait separate so that each gamete carries only one allele for each trait.

modern view of inheritence

the concept that genetic traits are passed from parents to offspring through discrete units called genes, which maintain their integrity across generations.

genotype vs phenotype

Genotype refers to the genetic makeup of an organism, while phenotype is the observable physical or biochemical characteristics determined by the genotype.

punnett squares

graphical method used to predict the genotypes and phenotypes of offspring from genetic crosses, illustrating the possible combinations of alleles.

continuous variation

results from the action of many genes to determine a characteristic like human height

discontinuous variation

traits that were inherited in distinct classes. refers to things like eye colour or blood group, which have a limited number of possible values

mendels model system

used garden pea to study inheritance

mendelian patterns of inheritence

the patterns of inheritance that follow the principles established by Gregor Mendel, including dominant and recessive traits.

historical views of inheritence

theories that predate Mendelian genetics, including blending inheritance and Lamarckism, which proposed different mechanisms for how traits are passed from one generation to the next.

gregor mendel

A scientist known as the father of genetics, who conducted experiments with garden peas to establish the basic principles of heredity.

hybridizations

mating two true breeding individuals that have different traits

first filial

offspring, daughter, or son

trait

defined as a variation in the physical appearance of a heritable characteristic

reciprocal cross

a paired cross in which the respective traits of the male and female in one cross become the respective traits of the female and male in the other cross

dominant traits

traits that are inherited unchanged in a hybridization

recessive traits

traits that become latent, or dissappear in the offspring of a hybridization

product rule

states that the probability of two independent events occuring together can be calculated by multiplying the individual probabilities of each event occurring along

sum rule

applied when considering two mutually exclusive outcomes that can come about by more than one pathway. states that the probability of the occurence of one event or the other event of two mutually exclusive events is the sum of their individual propabilities

alleles

gene variations that arise by mutation and exist at the same relative locations on homologous chromosomes

phenotype

observable traits expressed by an organism

genotype

an organisms underlying genetic makeup, consisting of both physically visible and non expressed alleles

homozygous

diploid organism that have two identical allels for that gene on their homologous chromosomes

heterozygous

genotype reflected that they have different alleles for the gene being examined

monohybrid

when fertilization occurs between two true breeding parents that differ in only one characteristic, resulting offsprings are monohybrids

two trait inheritence (dihybrid cross)

plants differing in two traitsare crossed, resulting in offspring that can display a combination of those traits. This method allows for the examination of the inheritance patterns of two distinct characteristics simultaneously.

law of independent assortment

the allele a gamete receives for one gene does not influence the allele received for another gene

human genetic disorders

are diseases caused by abnormalities in genes or chromosomes, which can be inherited or arise spontaneously.

tes cross

where dominant expressing organism is crossed with an organism that is homozygous recessive for the same characteristic. if the dominant expressing organism is homozygote then offspring will be heterzygotes expressing the dominant trait. if dominant expressing organism is heterozygote then offspring will be 1:1 ratio of heterozygotes and recessive homozygotes

pedigree analysis

used to study the inheritance pattern of human genetic diseases

incomplete dominance

a form of Gene interaction in which both alleles of a gene at a locus are partially expressed, often resulting in an intermediate or different phenotype. also known as partial dominance. an inheritance pattern where two alleles blend to create a new phenotype

codominance

a variation of incomplete dominance. where both alleles for the same characteristics are simulatneously expressed in the heterozygote

wild type

the gene, characteristic, or phenotype that occurs most frequently in the natural population

variants

what all other phenotypes and genotypes are considered when they are not considered a wild type

autosomes

any chromosome that is not a sex chromosome

x linked

when a gene being examined is present on the x chromosome but not on the y chromosome

hemizygous

describes a person who has only one copy of a gene rather than the usual two copies. men are considered this

human sex linked disorders

red-green color blindness and types a and b hemophilia

recessive lethal

an inheritance pattern in which an allele is only lethal in the homozygous form and in which the heterozygote may be normal or have some altered nonlethal phenotype

dominant lethal

where an allele is lethal both in the homozygote and heterozygote. this allele can only be transmitted if the lethality phenotype occurs after reproductive age. very rare, leads to death. eg huntingtons disease

law of dominance

states that in a heterozygote, one trait will conceal the presence of another trait for the same characteristic. rather than both alleles contributing to a phenotype, the dominant allele will be expressed exclusively.

law of independent assortment

states that genes do not influence each other with regard to the sorting of alleles into gametes, and every possible combination of alleles for every gene is equally likely to occur

dihybrid

a cross between two true breeding parents that express different traits for two characteristics

linkage

tendency for genes or other segments of DNA to be inherited together during meiosis because of their location near one another on the same chromosome

epistasis

interaction between gene is antagonistic, such that one gene masks or interferes with the expression of another

chromosomal theory of inheritance

identified chromosomes as the genetic material responsible for mendelian inheritance

made from the observations of theodor boveri (observed that proper sea urchin embryonic development does not occur unless chromosomes are present) and walter sutton (observed chromosome separation into daughter cells during meiosis)

consistent with mendel’s laws and explains how traits are passed from parents to offspring through the segregation and independent assortment of chromosomes.

homologous recombination

a type of genetic recombination in which nucleotide sequences are exchanged between two similar or identical molecules of DNA

nonparental types

are offspring that have different combinations of alleles than their parents, resulting from recombination during meiosis.

parental types

refers to offspring that inherit the same combination of alleles as their parents.

recombination frequency

is the percentage of recombinant offspring produced in a genetic cross, indicating the distance between genes on a chromosome. (average number of crossovers between two alleles)

centimorgans

is a unit of measure for genetic linkage, representing the distance between genes based on recombination frequency, where 1 centimorgan corresponds to a 1% chance of recombination occurring between two genes.

pedigree analysis

is a diagram that shows the occurrence and appearance of phenotypes of a particular gene or organism and its ancestors, used to track genetic traits and inheritance patterns.

amniocentesis

a prenatal test that uses a small sample of the fluid that surrounds the the fetus. test can diagnose genetic disorders (such as Down syndrome and spina bifida) and other health issues in a fetus

chroionic villi sampling

a prenatal test that utilizes either a catheter or needle to biopsy placental cells that are derived from the same fertilized egg as the fetus

karyogram

a visual representation of an individual's chromosomes, arranged in homologous pairs, used to analyze chromosomal abnormalities.

autosomes

the chromosomes that are not sex chromosomes, typically present in pairs in somatic cells, and involved in determining most of an individual's traits.

autosomal dominant disorders

huntington disease, poludactylyand achondroplasia, which are inherited in a dominant manner, meaning only one copy of the mutated gene is sufficient to express the disorder.

autosomal recessive disorders

PKU, albinism, sickle cell anemiaand cystic fibrosis, which require two copies of the mutated gene for the disorder to be expressed.

nondisjunction

a pair of homologous chromosomes has failed to separate or segregate at anaphase so that both chromosomes of the pair pass to the same daughter cell

risk of this occuring increases with the parents age and can result in conditions such as Down syndrome, Turner syndrome, or Klinefelter syndrome.

can occur during meiosis i or ii

euploid

an individual with the appropriate number of chromosomes for their species

aneuploid

is what an individual with an error in chromosome number is described as. can result from nondisjunction and leads to conditions such as trisomy or monosomy, affecting an individual's phenotype.

monosomy

condition in which only one chromosome from a pair is present in cells rather than the two copies usually found in diploid cells

trisomy

gaining an extraneous chromosomeresulting in three copies of a chromosome instead of the usual two, leading to genetic disorders.

polyploid

describes what individuals with more than the correct number of chromosome sets are called. this condition can lead to various phenotypic effects and is common in plants, often resulting in larger cell size and increased vigor.

x inactivation

the process by which one of the two X chromosomes in females is randomly silenced to prevent dosage imbalance of X-linked genes.

inactivates by tightly condensing into a quiescent (dormant) structure, or a barr body

chance that x chromosome in each cell inactivates in each cell is random, but once this occurs all cells derived from that one will have the same inactive x chromosome or barr bodh

pericentric

is an inversion and include the centromere

genetic counseling

is a process to help individuals understand genetic conditions, their risks, and the implications for themselves and their families.

barr body

a condensed, inactive X chromosome found in female mammals.

x linked alleles (Sex linked)

genes that carried on x chromosome, inheriteritence of y chromosome cannot offset the inheritence of an x linked recessive trait

human x linked recessive disorders

hemophilia a, color blindness, and others that are caused by mutations in genes on the X chromosome, primarily affecting males.

mitochondrial inheritence

a type of genetic inheritance where genes are passed from mother to offspring through mitochondrial DNA, affecting both males and females.

chromosomal pattersn of inheritance and variation

the transmission of genetic traits through chromosomes, including patterns of dominance, recessiveness, and linked genes.

polyploidy

a condition in which an organism has more than two complete sets of chromosomes, often leading to increased size and vigor in plants.

aneuploidy

the condition of having an abnormal number of chromosomes, either more or fewer than the typical diploid number.

disomic gametes

Gametes with two copies of a chromosome instead of one, resulting from nondisjunction during meiosis.

nullisomic gametes

Gametes with no copies of a particular chromosome, resulting from nullisomy (genome mutation where a pair of homologous chromosomes that would normally be present is missing)

monosomy

A genetic condition where an individual has only one copy of a chromosome instead of the normal two. This can lead to developmental issues and various health problems.

trisomy

A genetic condition where an individual has three copies of a particular chromosome instead of the usual two, resulting in an extra chromosome.

down syndrome

trisomy 21, due to nondisjunction of chromosome 21 during meiosis, leading to an extra chromosome that causes developmental and physical challenges. also due to translocation and maternal age

sex chromosome syndromes

abnormal number of x and/or y chromosomes, turner syndrome (XO), klinfelter syndrome (XXY)

deletion

a genetic mutation where a part of a chromosome or a sequence of DNA is lost during DNA replication, leading to potential genetic disorders.

translocation

a genetic rearrangement where a segment of one chromosome is transferred to another chromosome, potentially leading to genetic disorders.

inversion

a chromosomal rearrangement where a segment of a chromosome is reversed end to end.

human syndromes

cri du chat, robertsonian translocation (familiar down syndrome) disorders that lead to various developmental and physical issues.

gene

A segment of DNA that contains the instructions for building proteins or RNA molecules, essential for the functioning of living organisms.

chromosome

A structure within cells that contains DNA and carries genetic information. Chromosomes are essential for cell division and heredity.

genetic material

friffith with streptococcus pneumoniae concluded that virulence passed from dead strain to living strain

avery

found out that DNA is the transforming substance

structure of DNA

consists of two strands forming a double helix, with nucleotides containing a phosphate group, sugar, and nitrogenous bases.

chargaffs rules

amount of a, t, g, c in DNA varies from species to species but within a species, the amount of adenine (A) equals thymine (T) and the amount of guanine (G) equals cytosine (C)

DNA model

work of franklin and x ray diffraction that revealed the helical structure of DNA.

double helix model

sugar phosphate backbone, hydrogen bonded bases, phosphodiester bonds, 3’ end (-OH), 5’ end, the two strands are antiparallel from each other

criteria of genetic materia

The essential characteristics that genetic material must possess, including the ability to store information, replicate accurately, and undergo mutations.

dna levels of complexity

The organization of DNA from nucleotides to chromatin and chromosomes, including primary, secondary, and tertiary structures.

central dogma

DNA to RNA to protein, outlining the processes of transcription and translation.

DNA replication

each old strand of DNA serves as a template for the new replicated strandresulting in two identical DNA molecules.

semiconservative

where one old strand is conserved in each daughter molecule

steps of dna replication (prokaryotic)

unwinding by helicase→ DNA polymerase → single stranded binding proteins → topoisomerase → antiparallel strands