Chapter 2 Flashcards
life starts as a single cell called a
zygote
the single cell that is formed from the fusing of two gametes, a sperm and an ovum
zygotes
is distinct form any other human cell ever created and the cell contains genes that have passed down for 1000s of years
zygotes
all living things are composed of cells that promote growth and sustain life according to instructions in their molecule of
DNA
deoxyribonucleic acid
DNA
the molecule that contains the chemical instructions for cells to manufacture various proteins
DNA
Each molecule of DNA is called a
chromosome
contain units of instructions and consists of 46 chromosomes arranged in 23 pairs
chromosome
Chromosomes contain units of instructions called
genes
One of the 46 molecules of DNA (in 23 pairs) that each cell of the human body contains and that, together contain all the genes. Other species have more or fewer of these
chromosome
Each______ is located on a particular chromosome
gene
Additional _____and ______ another ______ surrounds each gene
DNA and RNA
A small section of a chromosome the basic unit for the transmission of heredity. A gene consists of a string of chemicals that provide instructions for the cell to manufacture certain proteins
gene
this material enhances, transcribes, connects, empowers, silences and alters genes
methylation
The nongenetic material used to be called junk but no longer
methylation
continues throughout life, and it can alter a gene’s expression even after a period is born, is a part of epigenetics.
methylation
the one important exception, every cell of each human being has copies of that person’s 46 chromosomes, arranged in 23 pairs, that one exception is
gamete
the reproductive cell
gamete
sperm in a man and ovum in a woman–has only 23 chromosomes, one from each of a person’s 23 pairs of chromosomes
gamete
A reproductive cell; that is a sperm or an ovum that can produce a new individual if it combines with a gamete from the other sex to form a zygote
gamete
At conception the ______ on each chromosome of the _____ match with ______ on the same chromosome of the ________
genes, sperm, genes, ovum
small variations or repetitions are called
copy number variations
any of the possible forms in which a gene for a particular trait can occur
allele
Every zygote inherits ______ from its sperm or ovum which means that
allele, many gene pits do not exactly match in every triplet
What occurs as the gametes form
mutation
For each individual, the collection of his or her genes is called the
genotype
a person’s actual appearance and behavior, reflects much more that the genotype
phenotype
is the beginning of diversity
genotype
is the actual manifestation of diversity
phenotype
only distinguishes each person
genetic diversity
the entire package of instruction that make a living organism is called the
genome
a worldwide effort to map all the human genes led to the
Human Genome Project
What was the first surprise of the Human Genome Project
that any two men or women of whatever ethnicity share 99.5 percent f their genetic codes
project aimed to spot all the variations in the human genome
HapMap
has found 11 million differences among the 3 billion possible chemical pairs of humans
HapMap
Why is HapMap research problematic
much remains to be understood about the connections between alleles in the genotype and actual characteristics of the phenotype. The sheer number of variations is daunting. scientist know that “genomics is not destiny.”
If genomic sequence determines anything behaviorally, it determines diversity.
each gamete consist of
23 chromosomes
means the child sex is not clear
ambiguous genitals
In 22 of the we pairs of human chromosomes that each person inherits, the chromosomes of each pair are closely match. They are called_______ and they could be inherited by male or female
autosomes
Two gametes (sperm and ovum) combine and produce a new individual with 23 chromosomes from each parent.
zygote
Genes are passed down from generation to generation.
Genotype and Phenotype
An organism’s genetic inheritance, or genetic potential
Unique for each organism
genotype
The observable characteristics of an organism, including appearance, personality, intelligence, and all other traits
phenotype
Genetic Variations and Similarities Overall
Many genes are identical for every human being.
Some genes vary slightly in their codes from one person to another.
Genetic Variations and Similarities Alleles
Variation of a gene or any of the possible forms in which a gene for a particular trait can occur.
Effects of variations vary greatly from causing life-threatening conditions to having no detectable effect at all.
Distinguishes each person
Allows the human species to adapt to pressures of the environment (e.g., climate changes, illnesses)
genetic diversity
Involves the full set of genes that are the instructions to make an individual member of a certain species
Similarity between two people: 99.5%
Similarity between humans and chimpanzees: 98%
Similarity between humans and every other mammal: 90%
genome
Found “only” about 20,000 genes in humans
Exact number is unknown
Human Genome Project
Involves international project trying to spot all variations in the human genome
Found 11 million variations among the 3 billion chemical pairs
HapMap
22 of 23 closely matched, human chromosomes
Can be inherited by a male or female
autosome
XX
XY
23 pair
a 23rd chromosome pair that consists of two X-shaped chromosome, one each from the mother and the father ____ zygotes becomes females
XX
A 23rd chromosome pair that consists of an X-shaped chromosome from the mother and a Y-shaped chromosome from the father_____zygotes become males
XY
Any given couple can produce four possible combinations of sex chromosomes; two lead to female children and two to male. True or False
True
In terms of the future person’s sex, it does not matter which of the mother’s Xs the zygote inherited.
True
All that matters is whether the father’s Y sperm or X sperm fertilized the ovum.
True
However, for X-linked conditions it matters a great deal because typically one, but not both, of the mother’s Xs carries the trait
True
The SRY gene not only directs the embryo to grow a penis, it also directs hormone production that affects the brain, skeleton, body fat, muscles, and much else from the moment of conception to the last breath in old age. influences that make for more sex differences than might be expected from .00005 of the genome.
True
Sex differences originate from one gene called one one chromosome
SRY
What is the one major exception to genetic diversity?
Although every zygote is generally unique not every newborn is, 1 in every 250 conceptions the zygote duplicates but splits apart completely creating two, or four, or even eight separate zygotes, each genetically identical to that first dingle cell
Each sibling gets abut 10,000 genes from each parent.
Millions of variations and billions of combinations are possible.
Full siblings are not necessarily alike.
sibling similarities
Originate from one zygote that splits apart very early in development
Incomplete split results in conjoined twins.
Same genotype but slight variations in phenotype are possible due to environmental influences.
Monozygotic twins
twins who originate from one zygote that splits apart very early in development. Also called identical twins
monozygotic twins
What does an incomplete split of the zygote create?
conjoined twins, formerly known as Siamese twins
Result from fertilization of two separate ova by two separate sperm.
Dizygotic twins have half their genes in common and occur twice as often as monozygotic twins.
Incidence is genetic and varies by ethnicity and age.
Dizygotic twins
twins who are formed when two separate ova are fertilized by two separate sperm at roughly the same time
dizygotic twins also know as fraternal twins
44 autosomes and 2 sex chromosomes
Females: XX
Males: XY
Sex of offspring depends on whether the father’s Y sperm or X sperm fertilizes the ovum.
Humans usually possess 46 chromosomes.
affected by many genes
polygenetic
influenced by many factors
multifactorial
Direct the interactions of other genes, controlling their genetic expression, duplication, and transcription
regulator genes
Genes that add something to some aspect of the phenotype
Add up to make the phenotype
Example
Height is affected by the contributions of about 100 genes.
additive genes
genes that do not contribute equal shares
non additive genes
one nonadditive form of heredity, alleles interact in a
dominant-recessive pattern
Dominant gene is far more influential than the recessive gene (non-additive).
Dominant gene can completely control the phenotype with no noticeable effect of recessive gene.
Effect of recessive genes can sometimes be noticed.
dominant-recessive heredity
the interaction of a pair of alleles in such a way that the phenotype reveals the influence of one allele (the dominant gene) more than that of the other (recessive gene)
dominant-recessive pattern
When someone inherits a recessive gene that is not expressed in the phenotype, that person is said to be
carrier of that recessive gene
A gene carried on the X chromosome. If a male inherits an X-linked recessive trait from his mother, he expresses that trait because the Y from his father has no counteracting gene. Females are more likely to be carriers of X-linked traits but are less likely to express them.
X-linked
If an _________ gene is recessive —as are the genes for most forms of color blindness, many allergies, several diseases ( including hemophilia and Duchenne ________ _________ and some ________ _________ the that it is on the ___________ is critical.
X-linked, muscular dystrophy, learning disabilities, X-chromosomes
