2. Mitosis and Meiosis (V)

Flashcards covering DNA structure, gene/allele concepts, mutation effects, protein synthesis, and meiosis/mitosis basics.

What is the basic unit of heredity?

A gene, a stretch of DNA on a chromosome that encodes instructions to build a protein.

What are the building blocks of DNA?

Nucleotides, each made of a sugar (deoxyribose), a phosphate, and a nitrogenous base.

Which bases pair in DNA?

Adenine (A) pairs with thymine (T); cytosine (C) pairs with guanine (G).These base pairs are held together by hydrogen bonds, forming the double helix structure of DNA.

How many chromosomes do human somatic cells have?

46 chromosomes.

What is a chromosome?

One long DNA molecule packaged with many genes along its length.

What is a locus?

The specific location of a gene on a chromosome; plural loci.

What are alleles?

Different forms of a gene with different DNA sequences.

What does diploid mean?

Two sets of chromosomes (2n) in a cell.

What does haploid mean?

One set of chromosomes (n); gametes are haploid.

What are homologous chromosomes?

Pairs carrying the same genes in the same locations and are the same type, though they may have different alleles.

What is a genotype?

The two alleles you have for a particular gene.

What is a phenotype?

The observable expression of the genotype.

What is a dominant allele?

An allele that is expressed in the phenotype even if the other allele is different.

What is a recessive allele?

An allele that is expressed only when an individual has two copies (homozygous recessive).

What is mutation?

A random change in the DNA nucleotide sequence that can create new alleles.

What is a nucleotide substitution?

Replacing one nucleotide with another in DNA.

What is a nucleotide insertion?

Adding an extra nucleotide into the DNA sequence.

What is a nucleotide deletion?

Removing a nucleotide from the DNA sequence.

What causes sickle cell disease?

A substitution mutation in the hemoglobin gene that changes the amino acid sequence and the protein's shape.

What is an enzyme?

A protein that speeds up a chemical reaction (biological catalyst).

What is transcription?

Copying a gene's DNA sequence into messenger RNA in the nucleus.

What is translation?

Reading the mRNA codons to assemble the amino acids into a polypeptide.

What is a polypeptide chain?

A chain of amino acids that folds into a functional protein.

What determines a protein's shape and function?

The sequence and bonding of amino acids determine how the chain folds into a specific shape that determines function.

What is DNA replication?

The process of copying DNA during S phase, producing two identical DNA molecules (sister chromatids).

What are sister chromatids?

Two identical DNA molecules attached at the centromere, formed during DNA replication.

What is mitosis?

Division of the nucleus producing two genetically identical diploid daughter cells.

What are the stages of mitosis?

Prophase (including prometaphase), Metaphase, Anaphase, Telophase; followed by Cytokinesis.

What is cytokinesis?

Division of the cytoplasm to form two separate cells.

What is the cleavage furrow?

An indentation that splits animal cells during cytokinesis.

What is the cell cycle?

The sequence of growth and division including G1, S, G2, M phases.

What happens in G1?

Growth; cells grow and perform normal functions.

What happens in S phase?

DNA replication; chromosomes are duplicated.

What happens in G2?

Preparation for mitosis; more organelles and cytoplasm are made.

What is meiosis?

Two cell divisions producing four haploid gametes from a diploid cell.

What is crossing over?

Exchange of genetic material between homologous chromosomes during prophase I.

What is recombination?

New combinations of alleles on chromosomes resulting from crossing over.

What is independent assortment?

Random orientation of homologous chromosome pairs at metaphase I.

How many possible combinations of maternal and paternal chromosomes are produced in humans due to independent assortment?

About eight and a half million per gamete.

What is a zygote?

The fertilized egg; a diploid cell formed by the union of sperm and egg.

DNA contains info for

building proteins and maintaining the organism, in other words the genetic blueprint essential for growth and development.

What is a locus?

specific physical location of a gene or other piece of DNA on a chromosome.