bio december genetics and cell division

Asexual reproduction

Reproduction involving a single parent producing genetically identical offspring

Advantages of asexual reproduction

1. No need to find a mate 2. Rapid reproductive cycle 3. Efficient in stable environments

Disadvantages of asexual reproduction

1. No genetic variation 2. Populations vulnerable to disease or environmental change

Sexual reproduction

Reproduction involving two parents producing genetically varied offspring

Advantages of sexual reproduction

1. Produces genetic variation 2. Can increase survival in changing environments

Disadvantages of sexual reproduction

1. Requires finding a mate 2. Slower reproductive process

Meiosis

Type of cell division producing four genetically different haploid gametes, each with half the number of chromosomes

Purpose of meiosis

1. Produce haploid gametes 2. Introduce genetic variation 3. Reduce chromosome number for sexual reproduction

Haploid

Cell containing a single set of chromosomes (n)

Diploid

Cell containing two sets of chromosomes (2n)

Mitosis

Type of cell division producing two genetically identical diploid cells for growth, repair, or asexual reproduction

Purpose of mitosis

1. Growth 2. Repair 3. Replacement of cells

DNA

Polymer made of nucleotides forming a double helix

Double helix

Two strands of DNA coiled together

Nucleotide

Molecule consisting of a sugar, phosphate group, and one of four bases (A, T, C, G)

Complementary base pairs

Specific base pairs joined by hydrogen bonds (A-T, C-G)

Hydrogen bond

Weak bond holding complementary bases together

Genome

Entire DNA of an organism

Gene

Section of DNA coding for a specific protein

DNA extraction practical

1. Mash fruit to break cell walls 2. Add detergent to break cell membranes 3. Add salt to help DNA precipitate 4. Filter to remove solids 5. Add cold ethanol to precipitate DNA 6. DNA appears as white stringy material

Protein

Molecule made of one or more polypeptides folded into a specific shape

Amino acid

Building block of proteins

Protein synthesis

Process of making a protein from a gene

Transcription

Process of copying a gene's DNA sequence into mRNA

Transcription process

1. RNA polymerase binds to non-coding DNA in front of gene 2. RNA polymerase separates DNA strands 3. RNA polymerase produces complementary mRNA from coding strand 4. mRNA detaches and leaves nucleus

Translation

Process of assembling a protein at the ribosome using mRNA

Translation process

1. mRNA attaches to ribosome 2. Ribosome reads codons (triplets of bases) on mRNA 3. tRNA brings corresponding amino acids 4. Amino acids linked by peptide bonds to form polypeptide chain 5. Polypeptide folds into functional protein

Codon

Triplet of bases on mRNA coding for a specific amino acid

Anticodon

Sequence of three bases on tRNA complementary to mRNA codon

tRNA

Transfer RNA, carries specific amino acids to ribosome during translation

RNA polymerase

Enzyme that synthesizes mRNA from DNA template

Non-coding DNA

DNA that does not code for proteins but can regulate gene expression

Effect of non-coding DNA variants

Can change RNA polymerase binding, altering protein quantity

Effect of coding DNA variants

Can change amino acid sequence, altering protein activity

Genetic variant

A change in the DNA sequence that can affect the phenotype

Mutation

Permanent change in the DNA sequence

Coding DNA

DNA that contains instructions to make proteins

Allele

Different version of the same gene

Dominant allele

Allele expressed in the phenotype even if only one copy is present

Recessive allele

Allele expressed in the phenotype only if two copies are present

Homozygous

Having two identical alleles for a gene

Heterozygous

Having two different alleles for a gene

Phenotype

Observable characteristics of an organism

Genotype

Genetic makeup of an organism

Polypeptide

Chain of amino acids linked by peptide bonds

Triplet

Sequence of three bases on DNA coding for a single amino acid

Complementary base pairing

Principle that A pairs with T and C pairs with G in DNA

DNA replication

Process by which DNA makes an identical copy before cell division

Semi-conservative replication

Each new DNA molecule contains one original strand and one newly synthesized strand

Helicase

Enzyme that unwinds and separates DNA strands during replication

DNA polymerase

Enzyme that adds complementary nucleotides to new DNA strand

Ligase

Enzyme that joins DNA fragments together

Chromosome

Long DNA molecule with associated proteins carrying genetic information

Chromatin

Loosely packed form of DNA in the nucleus

Protein coding gene

Section of DNA that codes for a polypeptide

mRNA

Messenger RNA, carries genetic code from DNA to ribosome

Transcription factors

Proteins that bind to non-coding DNA and regulate transcription

Gene expression

Process by which a gene's information is used to make a functional product

Meiosis function

Produces haploid gametes with genetic variation for sexual reproduction

Mitosis function

Produces diploid cells for growth, repair, and asexual reproduction

Comparison of mitosis and meiosis

1. Mitosis: 2 identical diploid cells, used for growth/repair 2. Meiosis: 4 genetically different haploid cells, used for sexual reproduction

Importance of meiosis

Increases genetic variation, reduces chromosome number for gametes

Importance of mitosis

Maintains chromosome number, allows growth and tissue repair

RNA

Ribonucleic acid, single-stranded nucleic acid involved in protein synthesis

Ribosome

Cell organelle where translation occurs and proteins are assembled

mRNA codon

Sequence of three bases on mRNA specifying one amino acid

tRNA anticodon

Sequence of three bases on tRNA complementary to mRNA codon

Peptide bond

Chemical bond linking amino acids in a polypeptide chain

Folded protein

Functional three-dimensional shape of a polypeptide, necessary for enzyme activity or structural function

Specific protein function

Depends on amino acid sequence and folding (e.g., enzymes, hormones, structural proteins)

Detergent in DNA extraction

Breaks down lipid membranes to release DNA

Salt in DNA extraction

Helps DNA molecules clump together and precipitate

Ethanol in DNA extraction

Precipitates DNA from solution for visualisation

Complementary base pairing in transcription

A pairs with U in RNA, C pairs with G

mRNA attachment to ribosome

Necessary step for translation

tRNA attachment

Brings specific amino acids to ribosome according to codon

Polypeptide formation

Amino acids linked in sequence to produce a protein

Genetic variants affecting phenotype

Non-coding DNA variants affect protein quantity; coding DNA variants affect protein structure and activity

Order of DNA bases determines amino acid sequence

the sequence of bases in a gene codes for the sequence of amino acids in a protein

Protein folding

amino acid sequence folds into a specific three-dimensional shape, essential for protein function

Functional proteins

proteins with a specific shape that determines their role (e.g., enzymes, structural proteins)

Transcription

process where RNA polymerase makes a complementary mRNA copy of a gene

Translation

process where ribosomes assemble amino acids into a polypeptide according to the mRNA code

mRNA codon

set of three bases on mRNA coding for a specific amino acid

tRNA anticodon - set of three bases on tRNA complementary to mRNA codon, bringing correct amino acid

Ribosome - organelle where translation occurs

Peptide bond formation - amino acids linked together to form a polypeptide chain

Effect of non-coding DNA variants - can alter RNA polymerase binding, changing amount of protein produced

Effect of coding DNA variants - can change amino acid sequence, altering protein activity