GEN BIO 2 | ETA Reviewer

Pedigree

a chart or diagram that shows how a trait or health condition is passed through generations of a family; helpful for analyzing the prominence of rare genetic conditions.

Genetics

the study of genes, which carry information that is passed from one generation to the next

Allele

variant form of a gene that is found in a specific location of the chromosome, known as the locus

Dominant Allele

the trait that masks the recessive allele, usually denoted by a capital letter

Recessive Allele

the trait masked by the dominant allele, usually denoted by a small letter

Law of Dominance

For a set of alleles, the dominant trait will be expressed.

Genotype

organism’s genetic information

Homozygous

possessing identical alleles of one gene, can be dominant homozygous or recessive homozygous depending on the allele present

Heterozygous

possessing different alleles of one gene, one dominant and one recessive

Phenotype

the observable physical traits

True-breeding

comes from the homozygous genotype, self-fertilization yields offspring with an identical trait.

Hybrid

comes from the heterozygous genotype, self-fertilization yields offspring with mixed genotypes and phenotypes

Pedigree Chart Parts | Square

it represents the male parent

Pedigree Chart Parts | Circle

it represents the female parent

Pedigree Chart Parts | Diamond

it represents an organisms whose sex is unknown

Pedigree Chart Parts | Shaded Shape

it represents an organism affected by the trait

Pedigree Chart Parts | Unshaded Shape

it represents a organism not affected by the shape

Pedigree Chart Parts | Marriage/mating lines

a horizontal line that connects the shapes that represent mates

Pedigree Chart Parts | Sibship Line

the lines connecting the siblings

Pedigree Chart Parts | Fraternal Twins

represented by the birthline branching out into the individual twin, diagonal lines are used

Pedigree Chart Parts | Identical Twins

it is similar to the fraternal twins but the twins are also connected by a horizontal line

Pedigree Chart Parts | Generation

these are labelled with roman numerals

Pedigree Chart Parts | Individuals

they are labelled with hindu-arabic numerals within one generation

Proband

the organism in the pedigree chart that is being studied or reported on and the first to report a certain trait in their family, usually indicated with an arrow

Propositus

a male proband

Proposita

a female proband

Law of Segregation

1. F1 parents (or the parental generation (PG)) contained two separate copies of each hereditary factor, which can be either dominant or recessive.

2. The factors separated when the gametes were formed. meaning an offspring will be carrying one allele from each parents.

3. Random fusion of all possible gametes occurred upon fertilization.

4. Two alleles for a heritable trait will split into segregate into different gametes

Law of Independent Assortment

• each pair of factors segregates or assorts independently of other pairs

• all possible combination of factors can occur in the gametes

Monohybrid Cross

a kind of punnett square used to test one trait

Dihybrid Cross

a kind of punnett square used to test two trait

Sex-linked Trait

the gene that determines the a character located on the sex chromosomes

X-linked Trait

a sex-linked trait is where the gene or allele for the trait in the X-chromosome

Y-linked Trait

a sex-linked trait is where the gene or allele for the trait in the Y-chromosome

Sex-influenced Trait

an autosomal trait in a diploid organism whose expression is affected by an individual’s biological sex and usually occurs at a higher frequency in one sex over the other

Sex-limited Trait

any autosomal trait that have genes occur in both sexes but are only expressed in one biological sex

Labeling Traits

the allele on the chromosome is shown as a letter attached to it

Mendelian Inheritance

the way in which genes and their corresponding traits are passed from the parents to offspring by means of dominant and recessive alleles

Non-Mendelian genetics

the pattern of inheritance where two alleles are neither dominant nor recessive

Co-dominance

two alleles of the same gene are expressed separately to yield different traits in an individual

Incomplete Dominance

a dominant allele does not completely mask the effects of a recessive allele, leading to the physical appearance showing a blending of both alleles

Intermediate Trait

the trait formed when incomplete dominance occurs

Multiple Alleles

there are more than two types of alleles for a given locus or trait, leading to more than two kinds of possible phenotypes for this trait

Monomer

the smallest unit of a polymer

Polymer

a long chain of molecule made of a repeating pattern of monomers

DNA

• Deoxyribonucleic Acid

• Double-stranded

• Has a deoxyribose structure (one carbon is connected to 2 hydrogen atoms)

• Has the nucleotide bases Adenine & Thymine and Cytosine & Guanine

• stores RNA and protein-encoding information, transfer to the next generation of cells

RNA

• Ribonucleic Acid

• Single-stranded

• Has a ribose structure (one carbon is connected to an hydrogen atom and a hydroxyl group)

• Has the nucleotide bases Adenine & Uracil and Cytosine & Guanine

• carries protein-encoding information, helps to make proteins, catalyzes reactions

Nucleotide

the monomer of a nucleic acid, is composed of a nitrogenous base, a five-carbon pentose sugar, and a phosphate group

Pyrimidines

has one ring, consists of the cytosine, thymine, and uracil

Purine

has double rings, consists of adenine and guanine

How Strands Link Together

• Two strands of DNA are linked together by hydrogen bonds between paired bases.

• Pairing a purine with a pyrimidine creates a uniform diameter for the helical shape of the DNA.

• These serve as the rungs of the DNA

Sugar-phosphate backbone

• The nucleic acids are connected via the phosphodiester bonds, connecting the phosphate group of one nucleotide and the sugar of another.

• A nucleic acid has an end at carbon 3, which has a hydroxyl group attached and an end at carbon 5, which has a phosphate group attached.

DNA

they have two strands pf polynucleotides forming a double helix in an antiparallel/complementary orientation

Minor Groove

the small bends in the DNA

Major Groove

the larger bends in the DNA

Base Pairings

• cytosine & guanine

• adenine & thymine (in DNA)

• adenine & uracil (in RNA)

• 5’ and 3’

Amino Acid

a molecule with an amino group, a carboxyl group, and a side group attached by an alpha carbon; there are 20 in total

codon

triplet code of bases, that code the protein to form a certain way for a specific amino acid

Protein Structure

analogous to a long strand of yarn, to the shape that can be knot from the yarn, and to the appearance of sweater made by the yarn

Primary Structure

the sequence of amino acids

Secondary Structure

fold and align themselves into A-helix and B-pleated sheet (with a repeating pattern

Random Coils

secondary structures with no repeating patterns

Tertiary Structure

3D arrangement overall shape of a polypeptide resulting from he interactions between the side chains of the various amino acids

Quartenary Structure

overall protein structure that results from the aggregation of these polypeptide subunits

mRNA

carries the genetic code from the DNA to the ribosome

Process of Making Protein`

1. Genes along the DNA molecule can direct the synthesis of mRNA.

2. mRNA moves into the synthesis of the cytoplasm via nuclear pore.

3. Protein polypeptides are synthesized using the information from the mRNA.

What is the consequence of a premature stop codon in an mRNA sequence

resulting protein is truncated and nonfunctional

What is the consequence during translation of a tRNA molecule carrying the wrong amino acid?

incorrect folding of DNA

Storage Proteins | Functions

stores amino acids

Storage Proteins | Examples

• casein, the source of amino acid in baby animals

• storage proteins in plant seed

• ovalbumin; proteins of egg whites for developing embryo

Defensive Proteins | Function

protect against disease

Defensive Proteins | Examples

antibodies inactivate and help destroy viruses and bacteria

Hormonal Proteins | Function

coordination of an organism’s activities

Hormonal Proteins | Example

insulin, a hormone secreted by the pancreas and causes other tissues to take up glucose and regulate blood sugar

Contractile and Motor Proteins | Function

movement

Contractile and Motor Proteins | Examples

actin and myosin proteins help muscles contract; motor proteins helps the cilia and flagella undulate

Structural Proteins | Function

support

Structural Proteins | Example

keratin in skin appendages; silk fibers in cocoons and webs; collagen and elastin in connective tissues

DNA Replication

• Also known as the semi-conservative replication, it is the process of making an identical copy of a DNA molecule to pass the genetic trait,

• The new DNA has one parent strand and one daughter strand.

• DNA elongates and slants in the 5’ to 3’ manner only.

DNA Replication as Semi-discontinuous

• The leading strand is synthesized continuously (5’ to 3’).

• The lagging strand is produced discontinuously in short stretches called Okazaki fragments.

Process of DNA Replication

1. The parental molecule has two complementary strands of DNA. Each base is paired by hydrogen bonding.

2. The two DNA strands are separated by the helicase enzyme to form a replication fork. Each strand is a template for a new complementary strand.

3. Single-strand binding proteins prevent the unwound strands from rejoining.

4. Topoisomerase untwists the double helix.

5. Primase makes a short stretch of RNA on the DNA template, called a primer

6. DNA Polymerase will add nucleotides complementary to the bases of the parental strand to form the new backbone of the strand. This replaces the RNA primer

7. The leading strand synthesizes continuously.

8. The lagging strand will synthesize discontinuously.

9. Exonuclease removes the RNA primer as the DNA Polymerase replaces it with the DNA strand

10. Ligase seals the sugar phosphate backbone, forming the phosphodiester bonds.

Helicase

an enzyme that separate the strands using hydrogen bonds

Single-strand binding proteins

They prevent the unwound strands from rejoining with one another.

Topoisomerase

it untwists the double helix

Primase

makes a short RNA primers on the DNA template to serve as guides as nucleotides will only attach to an existing strands

DNA Polymerase

adds DNA nucleotides to the RNA primer; only adds from the 5’ end to the 3’ end

Ligase

seals the sugar-phosphate backbone

Exonuclease

removes the RNA primer

Synthesis of Lagging Strand

Primase and DNA Polymerase take turns creating the RNA primer for one strand and creating the new DNA for it

Protein Synthesis

Genes along the DNA molecule can direct synthesis of RNA as it aids the in the synthesis of polypeptides in forming proteins.

mRNA | Full Name

Messenger RNA

mRNA | Definition

carries information that specifies a protein

rRNA | Full Name

Ribosomal RNA

rRNA | Definition

forms the ribosome where the site of protein synthesis occurs

tRNA | Full Name

Transfer RNA

tRNA | Definition

carries amino acid to the ribosome

Transcription

the process in the nucleus in which a gene’s DNA sequence is copied/transcribed to make the mRNA molecule through the attachment of free RNA bases

Base Pairings in Transcription

• Cytosine and Guanine pair with each other.

• Adenine pairs with Uracil.

• Thymine Pairs with Adenine.

Steps in Transcription

1. Initiation

2. Elongation

3. Termination

Initiation in Transcription

The enzyme RNA polymerase binds to the region of a gene called the promoter. The DNA unwinds to expose the nucleotides so the RNA polymerase can read it and make a complementary sequence of bases.

Elongation in Transcription

The RNA strand lengthens as the RNA polymerase adds the RNA nucleotides in a 5’ to 3’ direction.