Biol 1201 Exam 3 Review

Who are more likely to show sex linked recessive traits

Males

Result of meiosis

4 genetically distinct haploid cells

Haploid

A cell with one set of chromosomes (n)

Diploid

A cell with two sets of chromosomes (2n)

Gametes

Haploid reproductive cells (sperm and egg)

Somatic cells

Body cells that are diploid

Locus

The specific location of a gene on a chromosome

Pairs of chromosomes in humans

23 pairs (46 total chromosomes)

Autosomes

Non-sex chromosomes (22 pairs in humans)

Sex chromosomes

Chromosomes that determine sex (X and Y)

Karyotype

A picture showing all the chromosomes in a cell

Fertilization

Produces a diploid zygote

Meiosis I

Homologous chromosomes separate

Meiosis II

Sister chromatids separate

Crossing over

Exchange of DNA between homologous chromosomes

Crossing over location

At the chiasmata during Prophase I

Synapsis

Pairing of homologous chromosomes during Prophase I

Synaptonemal complex

A protein structure that holds homologous chromosomes together during synapsis

Unique events of meiosis I

Synapsis and crossing over, alignment of homologs at the metaphase plate, separation of homologs

Independent assortment

Random orientation of homologous chromosome pairs during meiosis I

Recombinant chromosomes

Chromosomes that contain DNA from both parents due to crossing over

Character vs. trait

A character is a general feature; a trait is a specific variation of that feature

Complete dominance

One allele completely masks another

Incomplete dominance

Heterozygotes show a blend of both traits

Codominance

Both alleles are fully expressed

Pleiotropy

One gene affects multiple traits

Epistasis

One gene affects the expression of another gene

Pedigree

A family tree showing the inheritance of a trait

Male symbol in pedigree

Square

Female symbol in pedigree

Circle

Filled-in symbol in pedigree

The individual shows the trait

Carrier for a recessive disorder

Only heterozygous individuals

Consanguineous mating

Mating between closely related individuals

Test cross

Used to determine an unknown genotype using a homozygous recessive organism

Law of segregation

Alleles separate during gamete formation

Multiplication rule

Used to find probability of two independent events both occurring

Addition rule

Used to find probability of either of two events occurring

Hemizygous gene

A gene found in only one copy, like on the X chromosome in males

SRY gene

Gene on the Y chromosome that triggers male development

Linked genes

Genes located close together on the same chromosome

Parental type offspring

An offspring with the same phenotype as the parents

Recombinant phenotype

An offspring with a new combination of traits not seen in parents

Maximum recombination frequency for unlinked genes

50%

Nondisjunction

Failure of chromosomes to separate properly during meiosis

Aneuploidy

Abnormal number of chromosomes

Monosomy

Missing one chromosome (2n - 1)

Trisomy

Having one extra chromosome (2n + 1)

Polyploidy

Having more than two sets of chromosomes

Deletion

Loss of a chromosome segment

Duplication

Repeating a chromosome segment

Inversion

Reversing the order of a chromosome segment

Translocation

Movement of a segment from one chromosome to another

Down syndrome cause

Trisomy 21

Monosomy X

The only viable human monosomy.

Mitochondrial DNA inheritance

Inherited from the mother.

Genomic imprinting

When a gene's expression depends on which parent it came from.

Griffith's mouse experiment

The experiment that showed transformation in bacteria.

Chargaff's two rules

1) DNA composition varies by species; 2) A = T and G = C.

Purines

Adenine (A) and Guanine (G).

Pyrimidines

Cytosine (C), Thymine (T), and Uracil (U).

Base pairs per turn of the DNA helix

10 base pairs.

Double helix model of DNA

Discovered by Watson and Crick.

Helicase

The enzyme that unwinds DNA.

Single-strand binding proteins

Keep DNA strands separated.

Topoisomerase

Relieves twisting strain in DNA.

Primase

Creates RNA primers to start replication.

DNA polymerase III

Adds new DNA nucleotides to the 3′ end.

DNA polymerase I

Replaces RNA primers with DNA.

DNA ligase

Joins Okazaki fragments together.

Leading strand

The strand synthesized continuously.

Lagging strand

The strand synthesized in fragments.

Okazaki fragments

Short DNA fragments made on the lagging strand.

Mismatch repair

Fixing errors missed during DNA replication.

Nucleotide excision repair

Process that removes damaged DNA using nuclease, polymerase, and ligase.

Eukaryotic DNA shape

Linear.

Prokaryotic DNA shape

Circular.

Telomeres

DNA sequences that protect chromosome ends.

Histones

Proteins that package and organize DNA.

Nucleosome

DNA wrapped around histone proteins.

Euchromatin

Loosely packed DNA that is transcriptionally active.

Heterochromatin

Densely packed DNA that is inactive.

Central dogma of biology

DNA → RNA → Protein.

Transcription

Process of making RNA from DNA.

Translation

Process of making a protein from mRNA.

Template strand

The strand that is the template for transcription.

Coding strand

The non-template strand.

Direction of mRNA synthesis

5′ to 3′ direction.

RNA polymerase

The enzyme that makes RNA.

Transcription location in eukaryotes

Nucleus.

Translation location

Cytoplasm (at the ribosome).

Promoter region in eukaryotes

TATA box.

Transcription factors

Proteins that help RNA polymerase bind to DNA.

Initiation of transcription

RNA polymerase binds to the promoter and unwinds DNA.

Elongation

RNA polymerase builds the RNA strand.

Termination

RNA polymerase stops transcription and releases RNA.

Introns

Noncoding sequences removed from pre-mRNA.

Exons

Coding sequences kept in mature mRNA.

RNA splicing

Removal of introns and joining of exons.

Spliceosome

Complex that removes introns from pre-mRNA.

Ribozymes

RNA molecules that act as enzymes.