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25 Cards in this Set

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Trait

A particular characteristic that a gene codes for.




-is inherited

Allele

A different form of the same gene.




Two alleles for the same gene would differ slightly in their nucleotide sequence.

Genotype

The combination of alleles that make up an individual

Phenotype

The observable traits of an individual.




Usually caused by a combination of genotype and environment.

Gene pool

All the alleles within a population.

Mutation

Apermanent change in a genetic sequence, including changes to the nucleotidesequence or chromosomal arrangement.

How do mutations occur?

They can occur spontaneously, or they are induced by a mutagen/environmental factor. They can also accidentally occur during DNA replication.

Germline mutations

Occur in gamete cells and hence can be passed on to the next generation.

Somatic mutations

Occur in body cells and cannot be passed on to the next generation.

Point mutations

Mutations in a gene involving the alteration/adding/removing of a single base in the DNA sequence.




Can be substitution or frameshift mutations.

Substitution

-Replacement of one nucleotide for another.


-Can be missense, silent or non-sense mutations.

Missense mutation

Causes the codon to read for a different amino acid. These mutations still produce a protein.

Silent mutation

Occurs when a substitution results in a new codon that still codes for the same amino acid.

Non-sense mutation

Whena substitution mutation results in the creation of a stop codon, it isclassified as a nonsense mutation, because no other amino acids will be addedafter this point.




These can have severe effects, especially if the stop codonis implanted early on, as they may not be able to fold correctly.

Frameshift mutations

Involve one or two nucleotides being either added (nucleotide insertion) or removed (nucleotide deletion) from a nucleotide sequence, altering every codon in that sequence from that point onwards.

Block/chromosomal mutations

Mutations that affect large sections of a chromosome, typically multiple genes. Can occur during meiosis or by mutagens.




There are five main types: duplication, deletion, inversion, insertion and translocation.

Duplication

involve the replication of a section of achromosome that results in multiple copies of the same genes on that chromosome

Deletion

removesections of a chromosome

Inversion

a section of the sequence breaks off the chromosome, rotates 180 degrees and reattaches to the same chromosome

Insertion

occurswhen a section of one chromosome breaks off and attaches to a differentchromosome.

Translocation

awhole chromosome or a segment of a chromosome becomes attached to or exchangedwith another chromosome.

Chromosomal abnormalities

-Involves a whole chromosome or part of a chromosome




-Can be detected by a karyotype




-Includes aneuploidy and polyploidy

Aneuploidy

The presence of an abnormal number of a particular chromosome




Can be either an extra chromosome (called a trisomy when there are three copies of one chromosome) or a missing chromosome.




Caused by non-disjunction during meiosis.





Polyploidy

-Where there are additional sets of chromosomes (more than two).




-Instead of diploid, it could be triploid or tetraploid etc.




-Can be caused by hybridization or diploid/haploid gametes (triploid) or diploid/diploid gametes (tetraploid) fusing.

Polyploidy: if the number of sets of chromosomes is....

-even, the organism is fertile




-odd, the organism is infertile