The Gene 2 Flashcards
chromosome
a threadlike structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes. Each chromosome consists of a DNA double helix bearing a linear sequence of genes, coiled and recoiled around aggregated proteins (histones). Their number varies from species to species: humans have 22 pairs plus the two sex chromosomes (two X chromosomes in females, one X and one Y in males). “Genes reside on chromosomes-long, filamentous structures buried within cells that contain tens of thousands of genes linked together in chains. Humans have 46 chromosomes in total – twenty-three from one parent and twenty-three from another.” (11)
genome
an organism’s entire set of DNA The entire set of genetic instructions carried by an organism is termed a genome (think of genome as the encyclopedia of all genes, with footnotes, annotations, instructions, and references). The human genome contains about between twenty-one and twenty-three thousand genes that provide the master instructions to build, repair, and maintain humans.” (11)
haploid
1 set of chromosomes. Sex Cells - called gametes - are haploid having the gametic number of chromosomes typically including one of each pair of homologous chromosomes — compare MD - hap/half. is it safe to say that with haploid the sex cell will receive 1/2 of its parent’s chromosomes, either parent’s mom, or parent’s dad? Diagram hap - half
diploid
2 sets of chromosomes, 1 inherited from each parent. non sex cells - called somatic - are diploid.
homologous
paternal and maternal pair of chromosomes that have the same genes at the same loci, but possibly different alleles.
allele
either of a pair (or series (pleiotropic) of alternative forms of a gene that can occupy the same locus on a particular chromosome and that control the same character
locus
the position on a chromosome of a particular gene.
dominant
is a relationship between alleles of one gene, in which the effect on phenotype of one allele masks the contribution of a second allele at the same locus.
recessive
an allele whose effect on phenotype is masked by a dominant allele or only expressed when an individual inherits two recessive alleles for a genes, one from each parent. For a recessive allele to produce a recessive phenotype, the individual must have two copies, one from each parent. An individual with one dominant and one recessive allele for a gene will have the dominant phenotype. They are generally considered “carriers” of the recessive allele: the recessive allele is there, but the recessive phenotype is not. - Women rarely go bald because like some men do because it is caused by a recessive allele located in a gene on the x chromosome. So it’s rare that women get 2 recessive alleles. But men need just one recessive allele. And that on their X chromosome, which they got from their mom. Mom got that allele on her X chromosome from either from her Dad or her Mom. So if you’re bald you blame it on your mother
genotype
the genetic constitution of an individual organism. Often contrasted with phenotype.
trait
Characteristics of an organism that are expressed by genes and/or influenced by the environment. Traits include physical attributes of an organism such as hair color, leaf shape, size, etc., and behavioral characteristics, such as bird nesting.
heterozygote
A person who has two different forms of a particular gene, one inherited from each parent. ex. ear wax. Mother received w and W. Dominant and recessive alleles for wet ear wax. She inherited two different versions of the same gene from each of her parents. When a person is heterozygous for a trait whichever allele is dominant will be expressed. So if someone inherited a heterozygous allele for hair color (Br) with ‘B’ denoting a dominant allele for brown hair and ‘r’ denoting a recessive allele for red hair, the dominant trait of brown hair would be expressed. MD. zygote - fertilized egg.
homozygote
A person who has two identical forms of a particular gene, one inherited from each parent. ex. two of the same allele. Dad received ww making his genotype homozygous recessive for this gene (wet ear wax)
punnet square
a diagram that is used to predict an outcome of a particular cross breeding experiment.
pleiotropy
one gene influences two or more seemingly unrelated phenotypic traits. ex. ear wax and body odor are produced by the same type of gland. Because this one gene has a multiple effects on traits or phenotypes, it’s an example of pleiotropic gene. the gene affects how wet your ear wax is and how much you stink.
autosomes
a chromosome that is not a sex chromosome. - we have 22 For example, humans have a diploid genome that usually contains 22 pairs of autosomes and one allosome pair (46 chromosomes total).
sex chromosome
a chromosome involved with determining the sex of an organism, typically one of two kinds. -ear wax picture
chromatin
a single, very long strand of DNA. It is spiraled up a bunch of times to be small.
chromatid
each of the two threadlike strands into which a chromosome divides longitudinally during cell division. Each contains a double helix of DNA.
polygenic trait
when one phenotypic trait is influenced by multiple genes working together.
pleiotropic trait
occurs when one gene influences two or more seemingly unrelated phenotypic traits
gene
a section of DNA on a specific location of a chromosome that contains information that determines a trait
Mendelian Trait
some single traits are decided by a single gene.
phenotype
the set of observable characteristics of an individual resulting from the interaction of its genotype with the environment.
somatic
any cell of a living organism other than the reproductive cells. non sex cells - diploid - 1 set from each parent
