WILD 4340 Exam 1

Gene Definition

Any segment of the DNA that codes for proteins

Allele Definition

Allele’s are the different variations of DNA at a particular locus

Locus Definition

The specific, physical location of a gene or other dna sequence on a chromosome

Nucleotide Definition

Basic chemical building block of nucleic acids like DNA & RNA

Base Pair Definition

Unit of two complementary nucleotides bonded together across opposite strands

Genotype Definition

An individuals complete genetic makeup or the specific set of alleles (genetic variants) carried at a particular location in the genome (genetic code)

Phenotype Definition

Can have multiple alleles within a single individual (color, size)

Heterozygote Definition

Allele’s at a particular gene or locus are different (Aa, Bb)

Homozygote Definition

Allele’s at a particular locus or gene are the same (BB, bb)

Independent Assortment Definition

Allele’s (gene variants) from two different genes will be inherited independently of one another

Pleiotropy Definition

Can have genes that influence several traits

Mutation Rate Definition

DNA replication errors generate mutations in most cells during replication

Law of Separation/Mendel’s First Law

Mendel found that different alleles could result in different phenotypes, and that these alleles could be inherited separately during reproduction

Meiosis Overview

• Diploid cells have two copies of each chromosome, one from each parent

• Chromosomes duplicated, does not change chromosome number

• Meiosis I separates homologous chromosomes

• Meiosis II separates that replicated chromosomes

• 4 Haploid cells, each with one chromosome from each homologous pair (parent)

How does Meiosis relate to Alleles

• Each homologous chromosome can carry a different allele for the same trait

• Meiosis I separates these alleles into different gametes

• Meiosis ends with one allele per locus within a gamete

Example: If blue chromosome has allele “A” and red has allele “a”, half of the gametes will have “A” and half will have allele “a”

Main takeaway/Results from Meiosis

• Meiosis results in four daughter cells (sperm,egg)

• Daughter cells have half the DNA content of the parent cell (daughter cells have haploid)

• Meiosis is important because in sexually reproducing organisms, cells from one individual joins with a cell from a second individual to create offspring

Mitosis Vs Meiosis

Mitosis

2 Daughter Cells

Chromosome number maintained

Generally genetically identical

No Recombination

Main Role of growth and repair

Meiosis:

4 Daughter Cells

Chromosome numbers halved

Not genetically Identical

Recombination Occurs

Main role gamete production

We are more focused on meiosis with animals because with evolution, the alleles are passed through generations

Central Dogma

Genetic information encoded in DNA is:

1. Transferred to messenger RNA via transcription

2. Transferred again into a protein sequence via translation

Information is never transferred from a protein back to DNA

Somatic Vs Germline Cells

Somatic: form body cells (majority of organisms)

• Mutations in somatic cells can be passed to daughter cells within the individual, but not inherited by the offspring

Germline: form gametes for the next generation (sperm + egg)

• Mutation in the germline cells can enter a gamete and therefore be inherited by offspring

What are the 3 types of mutants?

1. Morphological Mutants

2. Lethal Mutants

3. Conditional Mutants

What are the effects of Morphological mutants?

Mutations that change the visible features of an organism: size, shape, color, etc

What are the effects of Lethal mutants?

Causes premature death of an organism

• Occurs at any life stage, often early

• Usually recessive, meaning an organism would need to have two copies of the mutated allele (homozygous) for the premature death to occur

What are the effects of Conditional mutants?

Interaction between environmental conditions and a genotype results in different phenotypes

• Siamese cats have a temperature sensitive fur color, where cooler body parts are darker than warmer areas

What is Cell Partitioning?

In most multicellular organisms (but not plants), cells are divided into two groups early in development

1. Somatic (form body cells)

2. Germline (form gametes for the next generation, sperm + egg)

What are point mutations?

• Every DNA replication provides another opportunity for a replication error

Female Germline: cells that ultimately produce eggs undergo a relatively limited number of cell divisions

Male Germline: spermatogonial stem cells continue dividing to produce sperm, as males age, the lineage leading to a sperm has undergone progressively more DNA replications

• Sperm generally contribute more new point mutations to offspring than eggs and the number increases with paternal age