BIOL 101 Final

Gene

A specific segment of the DNA that directs the synthesis of a protein, which in turn plays a structural or functional role within the cell. By coding for a specific protein, a gene determines the expression of a characteristic or trait.

Trait

A specific, heritable characteristic or attribute of an organism, often determined by its genes.

Alleles

Is a variant form of a gene. Each individual inherits two alleles for a specific gene, one from each parent. Two of the same alleles are called homozygous. Two different alleles are called heterozygous.

Locus

Refers to the specific, fixed position of a gene or genetic marker on a chromosome.

Homozygous

Individuals with two copies of the same allele of a gene.

Heterozygous

Individuals with different alleles of a given gene.

Dominant allele

When the effects of a certain allele can be detected regardless of whether an alternative allele is present, meaning it will express its phenotype in both homozygous and heterozygous conditions.

Recessive allele

An allele whose effects are masked in the in the heterozygous condition.

Genotype

Is the precise set of alleles a person possesses for a given trait or traits. It tells whether the individual is homozygous or heterozygous for a given gene.

Phenotype

Is the observable physical traits of an individual.

Pedigree

A chart showing the genetic connections between individuals in a family, can be used to deduce the unknown genotype by looking at the expression of the trait in the person’s ancestors.

Main difference between mendelian and non-mendelian inheritance

The simplicity of their inheritance patterns. Mendelian traits are governed by a single gene with two alleles dominant and recessive, following predictable inheritance patterns. While non-mendelian traits exhibit more complex inheritance patterns that don’t adhere to simple rules, often involving multiple genes & alleles.

Two examples of mendelian traits

1.Eye color. 2. Dimples

Two examples of non-mendelian traits

1. Blood type. 2. height.

5 types of non-mendelian inheritance. 2 & 5 have Ex:

• Incomplete dominance: Neither allele for a trait is completely dominant, resulting in a phenotype that is a blend of the two homozygous phenotypes.

• Codominance: Occurs when both alleles for a trait are expressed equally in the heterozygous phenotype Ex: AB blood.

• Pleiotrophy: One gene leading to many effects Ex: sickle-cell anemia.

• Multiple alleles: Refers to where more than two alleles for a single gene exist within a population. Ex: ABO blood types.

• Polygenetic inheritance: The involvement of two or more genes, often on different chromosomes, in producing a trait. The more genes involved the smoother the gradations and the greater the extremes of trait expression.

Deletion

Is the loss of a piece of chromosome. Breakage can be caused by certain chemicals, radiation, or viruses. Or when one chromatid loses a segment, and another will have gained a segment.

Potential consequences of deletion Ex: of syndrome

Deletion of more than a few genes on an autosome is usually lethal. Cri-du-chat syndrome (improperly developed larynx due to deletion) causes severe mental impairment.

Duplication

Is the addition of a piece of chromosome. The effects depend on its size and position, a small duplication is less harmful than a deletion of the same size.

Potential consequences of duplication Ex: of syndrome

Fragile X syndrome: causes abnormal facial features, mental impairment.

Structure of DNA 4 types

DNA contains four types of nitrogenous bases: Adenine (A), Guanine (G), Thymine (T), and cytosine (C). Double helix ladder: The sides of the ladder are composed of alternating sugars & phosphates. The rungs are consist of paired nitrogenous bases.

Rules of complementary base pairing

Adenine pairs ONLY with Thymine (A-T pair), Cytosine pairs ONLY with Guanine (C-G pair), each pair is held together by weak hydrogen bonds.

Semiconservative replication

Each strand of the original DNA molecule serves as a template for the formation of a new strand, in each of the new double-stranded DNA molecules, one original (parent) strand is saved (conserved), and the other (daughter) strand is new.

How does DNA replication begin?

Begins when an enzyme breaks the weak hydrogen bonds that hold together the paired bases that make up nucleotide strands of the double helix, thereby “unzipping” and unwinding the strands.

What part of the DNA is a template for DNA replication

The nitrogenous bases on the separated regions of each strand (Both parental strands) are temporarily exposed serving as templates for new strands.

Where do the nucleotide bases for new DNA strands come from?

Free nucleotides, which are always present within the nucleus, link to complementary bases on each new DNA strand.

3 examples of the role of enzymes in DNA replication

DNA polymerase unwinds the DNA helix, synthesizes new DNA strands, and joins them together.

How are DNA and RNA different? 4 reasons each

DNA is double-stranded, contains deoxyribose sugar, uses thymine, and functions primarily in the nucleus; RNA is single-stranded, contains ribose sugar, uses uracil, and functions primarily in the cytoplasm.

How are DNA and RNA the same? 4 reasons

Both are nucleic acids, composed of linked nucleotides, have a sugar-phosphate backbone, and have four types of bases.

What are the 3 types of RNA?

mRNA, tRNA, rRNA

What is transcription?

DNA message, copy message as RNA, convert to protein