bio

What happens during fertilization?

A sperm cell and an egg cell combine to form a zygote.

How many chromosomes do humans have?

Humans normally have 46 chromosomes, arranged in 23 pairs.

What is a chromosome?

A structure made of DNA and proteins that carries genetic information.

What is a gene?

A segment of DNA that contains genetic information.

What is a haploid cell?

A cell with one set of chromosomes; human haploid cells have 23 chromosomes.

What is a diploid cell?

A cell with two sets of chromosomes; human diploid cells have 46 chromosomes.

What is the cell cycle?

The series of events a cell goes through as it grows and divides.

What is mitosis?

Cell division that produces two genetically similar cells.

What is meiosis?

Cell division that produces four haploid cells.

What is the main difference between mitosis and meiosis?

Mitosis produces 2 cells and meiosis produces 4 haploid cells.

What is a karyotype?

An organized display of an individual's chromosomes.

What is nondisjunction?

The failure of chromosomes to separate properly during cell division.

What is an example of a disorder caused by nondisjunction?

Down syndrome, which is commonly caused by an extra copy of chromosome 21.

What does homozygous mean?

Having two identical alleles, such as AA or aa.

What does heterozygous mean?

Having two different alleles, such as Aa.

What is an allele?

An alternative form of a gene.

What is a dominant allele?

An allele that can determine the phenotype when only one copy is present.

What is a recessive allele?

An allele whose phenotype generally appears when two recessive copies are present.

What is a genotype?

The genetic makeup or allele combination of an organism.

What is a phenotype?

The observable characteristics of an organism.

What is pleiotropy?

When one gene affects multiple traits.

Who was Gregor Mendel?

A scientist whose pea plant experiments helped establish basic principles of inheritance.

What is a Punnett square?

A diagram used to predict possible genetic combinations in offspring.

What is a pedigree chart?

A diagram used to track the inheritance of a trait through a family.

What is complete dominance?

One allele completely masks the effect of another allele.

What is incomplete dominance?

The heterozygous phenotype is intermediate between the two homozygous phenotypes.

What is codominance?

Both alleles are expressed in the heterozygote.

What are the ABO blood types?

A, B, AB, and O.

What genotype produces type A blood?

IAIA or IAi.

What genotype produces type B blood?

IBIB or IBi.

What genotype produces type AB blood?

IAIB.

What genotype produces type O blood?

ii.

Why is AB blood an example of codominance?

Both the IA and IB alleles are expressed.

What is polygenic inheritance?

When multiple genes influence one trait.

What is a sex-linked gene?

A gene located on a sex chromosome.

Why are sex-linked disorders important?

Genes on sex chromosomes can have different inheritance patterns in males and females.

What is chromosome deletion?

A chromosome mutation in which a section is removed.

What is chromosome duplication?

A chromosome mutation in which a section is copied.

What is chromosome inversion?

A chromosome mutation in which a section of a chromosome is reversed.

What is chromosome translocation?

A chromosome mutation in which a section moves to another chromosome.

What is DNA?

Deoxyribonucleic acid; the molecule that stores genetic information.

What is RNA?

Ribonucleic acid; a molecule involved in using genetic information to make proteins.

What sugar does DNA contain?

Deoxyribose.

What sugar does RNA contain?

Ribose.

What bases are found in DNA?

Adenine, thymine, cytosine, and guanine.

What bases are found in RNA?

Adenine, uracil, cytosine, and guanine.

How do DNA bases pair?

A pairs with T and C pairs with G.

How does RNA base pairing work?

A pairs with U and C pairs with G.

What is DNA replication?

The process of copying DNA.

What does semiconservative replication mean?

Each new DNA molecule contains one original strand and one newly made strand.

What is mRNA?

Messenger RNA; it carries genetic information from DNA to the ribosome.

What is tRNA?

Transfer RNA; it brings amino acids to the ribosome.

What is rRNA?

Ribosomal RNA; it forms part of the ribosome and helps with protein synthesis.

What is gene expression?

The process by which information in a gene is used to produce a functional product.

What is transcription?

The process of making RNA from a DNA template.

How is mRNA modified?

The initial RNA transcript is processed by adding a 5' cap and poly-A tail and removing introns.

What is an intron?

A section removed from pre-mRNA during RNA processing.

What is an exon?

A section retained in mature mRNA after RNA processing.

What is translation?

The process of using mRNA information to make a protein.

What is a codon?

A sequence of three nucleotides on mRNA that specifies an amino acid or signal.

What is the start codon?

AUG.

What is a mutation?

A change in the DNA sequence.

What is a substitution mutation?

One nucleotide is replaced by another.

What is an insertion mutation?

One or more nucleotides are added.

What is a deletion mutation?

One or more nucleotides are removed.

What is a frameshift mutation?

An insertion or deletion that changes the reading frame.

What is genetic engineering?

The deliberate manipulation of an organism's genetic material.

What is recombinant DNA?

DNA created by combining genetic material from different sources.

What does a restriction enzyme do?

It cuts DNA at specific sequences.

What does DNA ligase do?

It joins DNA fragments together.

What is gene therapy?

An approach that uses genetic material or genetic modification to help treat a disease.

What is genomics?

The study of genomes and genetic information on a large scale.

What is the basic flow of genetic information?

DNA → RNA → Protein.

What is the difference between transcription and translation?

Transcription is DNA → RNA; translation is mRNA → protein.

What is the difference between pleiotropy and polygenic inheritance?

Pleiotropy is one gene affecting many traits; polygenic inheritance is many genes affecting one trait.

What is the difference between genotype and phenotype?

Genotype is genetic makeup; phenotype is observable characteristics.

What is the difference between homozygous and heterozygous?

Homozygous means the alleles are the same; heterozygous means they are different.