Bio Unit 3 study guide

Law of Segregation

During Meiosis, the two alleles for a gene separate when homologous chromosomes are pulled apart in Anaphase I, so each gamete gets only one allele

Law of Independent Assortment

Different pairs of homologous chromosomes line up randomly during Metaphase I of meiosis, so genes on different chromosomes are inherited independently of each other

Allele

A different form of the same gene

Dominant Allele

An allele that is expressed when at least one copy is present

Recessive Allele

An allele that is only expressed when two copies are present

Genotype

The genetic makeup of an organism

Phenotype

The physical traits that are expressed from the genotype

Punnett square

A diagram used to predict the possible genotypes and phenotypes of offspring from a genetic cross

Autosomal dominant traits

Appears in every generation

Autosomal recessive traits

Can skip generations

Inheritance, symptoms, and physiological traits of TaySachs disease

Autosomal recessive

Developmental delay, muscle weakness, vision/hearing loss, early death

Harmful lipids build up in brain cells due to missing enzyme, causing nerve cell damage

Inheritance, symptoms, and physiological traits of Cystic Fibrosis disease

Autosomal recessive

Thick mucus in lungs, frequent lung infections, digestive problems

Defective protein causes abnormal salt and water movement, producing thick, sticky mucus

Inheritance, symptoms, and physiological traits of Sickle Cell disease

Autosomal recessive

Pain episodes, anemia, fatigue, organ damage

Red blood cells become sickle shaped and block blood flow, reducing oxygen delivery

Inheritance, symptoms, and physiological traits of Huntington disease

Autosomal dominant

Uncontrolled movements, memory loss, personality changes

Mutated gene causes gradual breakdown of nerve cells in the brain

Incomplete dominance

The heterozygous phenotype is a blend of both alleles

Codominance

Both alleles are fully expressed at the same time

Polygenic inheritance

A pattern of inheritance in which multiple genes control a single trait

Special characteristics of inheritance of alleles of the ABO blood group

Multiple alleles

Codominance

Recessive allele

How can the environment influence genetic traits

Can affect how genes are expressed, changing the phenotype without changing the genotype

Linked genes

Genes that are located close together on the same chromosome and tend to be inherited together during meiosis, rather than sorting independently

X linked inheritance

A pattern where the gene causing a trait or disorder is located on the X chromosome

Inheritance, symptoms, and physiological traits of Duchenne muscular dystrophy

X linked recessive

Progressive muscle weakness, difficulty walking, frequent falls, enlarged calf muscles

Lack of dystrophin protein causes muscle fibers to break down and weaken over time

Inheritance, symptoms, and physiological traits of Hemophilia

X linked recessive

Excessive bleeding, easy bruising, prolonged clotting after injury

Missing or defective clotting factor proteins prevent blood from clotting normally

How chromosome number disorders arise

When there is an extra or missing chromosome

Chromosomal cause and symptoms of Down Syndrome

Trisomy 21

Intellectual disability, distinct facial features, heart defects, short stature

Chromosomal cause and symptoms of Turner Syndrome

Monosomy X

Short stature, webbed neck, infertility, heart defects

Chromosomal cause and symptoms of Klinefelter Syndrome

XXY in males

Tall stature, small testes, reduced testosterone, infertility, sometimes learning difficulties

Chromosomal cause and symptoms of Poly X Females

Extra X chromosome(s)

Often taller than average, sometimes learning difficulties, usually normal fertility

Chromosomal deletion

A chromosome loses a segment, removing genes

Chromosomal duplication

A chromosome has an extra copy of a segment, repeating some genes

Chromosomal translocation

A segment of one chromosome breaks off and attaches to a different chromosome

Chromosomal inversion

A chromosome segment breaks off, flips, and reattaches, reversing the gene order

Two observations Darwin made on his voyage

Variation among species

Adaptation to environment

Lamarck’s explanation as to how evolution might happen

Traits acquired during an organism’s life are passed to offspring

Darwin’s explanation as to how evolution might happen

Natural selection favors individuals with traits that increase survival and reproduction

Biological evolution

The change in inherited traits of a population over generations, leading to the development of new species or adaptations

Four lines of evidence for evolution

Fossil record

Comparative anatomy

Embryology

Molecular biology

Five conditions necessary for the allele frequencies in a population to be in Hardy Weinberg equilibrium

No mutations

Random mating

No natural selection

Extremely large population

No gene flow

Mutation

Random changes in DNA that creates new alleles, introducing genetic variation

Gene flow

Movement of alleles between populations, adding or removing genes

Genetic drift

Random changes in allele frequencies, especially in small populations

Natural selection

Differential survival and reproduction based on advantageous traits

Nonrandom mating

Individuals with preferred traits mate more often, changing allele frequencies

Allopatric speciation

Geographic isolation

Sympatric speciation

Same area, no physical barrier

Parapatric speciation

Partial speciation

Theory of evolution

Explains that all species share common ancestry and change over time

Phylogenetics

Uses evolutionary relationships to create diagrams showing how species are related

Classification of organisms

Organizes species based on shared traits and evolutionary history

Microbiota

The collection of microorganisms that naturally live in or on a specific environment in the body

Beneficial effects of microbes

Digestion and nutrient absorption

Food production

Biotechnology and medicine

Environmental roles

Protection against harmful microbes