Chapter 2 - Biological and Environmental Foundations Flashcards Preview

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Flashcards in Chapter 2 - Biological and Environmental Foundations Deck (100)
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Characteristics of your phenotype, such as your height, are determined by a combination of your ____________ and your ____________

genotype and your environment


Phenotype vs. Genotype

Phenotype – the directly observable characteristics Genotype - the complex blend of genetic information that influences our unique characteristics


Deoxyribonucleic acid (DNA)

long, double-stranded molecules that make up chromosomes


The ‘rungs’ on the (DNA) ladder are made up of …

The ‘rungs’ on this ladder are made up of four bases Adenine (A) Thymine (T) Guanine (G) Cytosine (C) The pairings are always A-T and C-G



A segment of a DNA molecule that contains hereditary instructions Genes can be of different lengths, varying from maybe 100 to thousands of base pairs It’s been estimated that we have 20,000 to 25,000 genes • We share between 98% and 99% of these with the chimpanzee • You share about 99.1% of your genes with the person sitting next to you



The process of cell duplication, in which each new cell receives an exact copy of the original chromosomes This is how body cells reproduce



human sperm and ova, which contain half as many chromosomes as regular body cells


Meiosis And the steps

the process of cell division through which gametes are formed and in which the number of chromosomes in each cell is halved Steps 1. Chromosomes each duplicate and then pair up with one another 2. Crossing over takes place between the two innermost pair members 3. The pairs of chromosomes separate to form two cells, each with 23 duplicated chromosomes 4. The duplicated chromosomes separate to form gametes each with 23 single chromosomes This results in 4 sperm or 1 ovum



When gametes unite at conception



The area surrounding the cell nucleus, where the genes send instructions for an assortment of proteins


Crossing over during meiosis

When chromosomes next to each other break at one or more points along their length and exchange segments, so that genes from one are replaced by genes from the other. This increases genetic diversity.



the 22 matching chromosome pairs in each human cell they are numbered from longest to shortest


Sex chromosomes

The 23rd pair of chromosomes, which determines the sex of the child In females, we see XX; in males, we see XY The X chromosome is significantly larger than the Y, and carries more genetic material


Fraternal, or dizygotic, twins

Twins resulting from the release and fertilization of two ova. They are genetically no more alike than ordinary siblings


Maternal factors linked to fraternal twinning

Ethnicity Family history of twinning Age (rise with age peaking at 35-39) Nutrition (more often with tall and/or normal to overweight) Number of births (more likely with each additional birth) Fertility drugs and in-vitro fertilization Climate


Identical, or monozygotic, twins

Twins that result when a zygote, during the early stages of cell duplication, divides in two. They have the same genetic makeup


Multiple birth children are often …

born early, and are thus often less healthy and slower to develop in the early years than are single birth children



Each of two forms of a gene located at the same place on the autosomes A pair can be homozygous or heterozygous


Dominant-recessive inheritance

a pattern of inheritance in which, under heterozygous conditions, the influence of only one allele is apparent The allele that is apparent in heterozygous conditions is referred to as dominant The one that is apparent only in the homozygous condition is referred to as recessive


Recessive carrier

A heterozygous individual is a carrier for the recessive trait


Phenylketonuria or PKU

One of the most frequent occurring recessive disorders. It effects how the body breaks down proteins in many foods. By year one infants with PKU are permanently restarted if not treated. If treated they still show some issues with certain cognitive skills but they will have an average intelligence and life span.


Modifier genes

Genes that can enhance or dilute the effects of other genes Thus, even if two siblings inherit a given gene from their parents, they may display the trait to different extents


It’s ______ for serious diseases to be due to _______ alleles

It’s rare for serious diseases to be due to dominant alleles


Huntington Disease

An example of the rare dominant disorders. It is a condition where the nervous system degenerates. It occurs because the symptoms do not occurs to the age of 35 or later.


Incomplete dominance

a pattern of inheritance in which both alleles are expressed in the phenotype, resulting in a combined trait, or one that is intermediate between the two An example here is sickle cell anemia Individuals who are heterozygous show symptoms under conditions of oxygen deprivation, such as during intense exercise or at high altitudes


x-linked inheritance

When a harmful allele is carried on the x chromosome Males are more likely to be affected because they don’t have another x chromosome to have an allele that could be dominant and counter act it.



A disorder that is x-linked in its inheritance Blood fails to clot normaly.


Genomic imprinting (aka genetic imprinting)

A pattern of inheritance in which alleles are imprinted, or chemically marked, in such a way that one pair member is activated, regardless of its makeup This is often temporary; the imprinting may be erased in the next generation, and doesn’t seem to occur in everyone Examples include an increased likelihood of inheriting diabetes from one’s father and an increased likelihood of inheriting asthma or hay fever from one’s mother


Prader-Willi syndrome

A disorder with symptoms of mental retardation and severe obesity Genomic imprinting is involved


Mutation Germline mutation Somatic mutation

A sudden but permanent change in a segment of DNA Some mutations affect single genes, while others affect multiple genes One well-known cause of mutations is ionizing radiation exposure in either parent Germline mutation takes place in the cells that will produce gametes Somatic mutation takes place in body cells and can occur any time in life