Unit 5: Genetics

Structure of a DNA is based on a ________ composed of a sugar, a phosphate group, and a nitrogen base.

A single DNA molecule can be thousands of base pairs in length

nucleotide

Double helix structure of DNA was discovered by James ______ and Francis ______. However, Rosalind Franklin did a lot for this discovery.

watson, crick

1. DNA wraps around protein to make ______

2. These fold up to make ________

3. These are then duplicated

4. The number of these per cell varies by species

Chromatin, chromosomes

Most of the time, DNA exists as _____. Chromosomes condense and form only during cell division (______) process.

chromatin, mitosis

A pictorial depiction of an organisms chromosome complement is called a ______. It involves photographing chromosomes during mitosis then lining them up for examination.

Karyotype

On the 23rd pair of chromosomes, sex is defined. Males: ____, Females: ____

XY, XX

UV ______ can penetrate living cells and alter the structure of a DNA molecule. The resulting structural alteration is called a _____ ________.

radiation, point mutation

The _____ and ______ of nitrogen bases are important to the integrity of the DNA molecule and any resulting proteins. Sometimes alterations in structure can cause abnormal base pairings (A with G or C with T).

number, sequence

______ can:

• Alter DNA structure

• Be passed to new cells

• disrupt the ______ process of protein synthesis

mutations, transcription

_________ on a chromosomal level can cause sections of the chromosome (genes) to be

• Deleted

• Inverted

• Duplicated

  • Can cause _____ _____

• Translocated

Issues in chromosome number (3 copies of chromosome #21 instead of 2) can result in ____ _______

mutations, Huntington disease, down syndrome

Disorders related to the sex chromosomes (specifically x) include:

______: Can’t produce blood-clotting proteins

Red-green _____ _____: Can’t differentiate between the two colors

____ are more vulnerable because there’s only one x chromosome

hemophilia, color blindness, males

_______ is the type of cell division by

which gametes (eggs and sperm) are

produced.

Meiosis

• Offspring that result from sexual

reproduction are _______ (having one set of genes from

the father and one set from the mother).

• At fertilization, an egg cell and sperm cell, each

carrying a set of genes (chromosomes) are united.

• If two diploid cells united, then the result would be a _______ cell.

diploid, quadroploid

One of the important features of meiosis is that it

reduces the number of chromosomes by ____.

• _____ cells become _____ cells, since meiosis involves two rounds of division, it actually produces four daughter cells.

• When the haploid cells join at _______ (egg cell and sperm cell), the

  diploid condition is restored

half, diploid, haploid, fertilization

Two phases of ______:

Prophase I, Metaphase I, Anaphase, Telophase I

Prophase II, Metaphase II, Anaphase II, Telophase II

meiosis

______ I:

Each chromosome duplicates and remains linked (two sister chromatids).

Crossing over can occur during this stage.

________ chromosomes come together, forming ______.

Crossing over or ________ can occur at this stage.

• This is an important source of genetic _____ in sexually reproducing organisms

Prophase, homologous, tetrads, recombination, variation

______ I:

_______ chromosomes align at the ________ plate. This alignment is completely random and is known as ________ assortment. This is another source of genetic ______.

metaphase, homologous, equatorial, independent, variation

_____ I

________ pairs separate with sister chromatids remaining together. Another source of genetic variation.

Anaphase, homologous

_________I:

____ daughter cells are formed with each daughter containing only ____

chromosome of the _______ pair.

_____ __, if distinguished at all,

proceeds immediately. DNA does not replicate a second time.

telophase, two, one, homologous, prophase II

Second division of ______:

_____(sex cell) formation

The second round of meiotic division is essentially

like mitosis, except the cells are ______(n)

instead of diploid (2n).

meiosis, gamete, haploid

_______ II:

Chromosomes (sister chromatids) align at the

equatorial plate.

metaphase

______ II

Chromosomes (sister chromatids) migrate

separately to each pole.

anaphase

______ II

Cell division is complete. _____ haploid daughter cells are obtained. Note that each is genetically ______.

telophase, four, different

_____ produces ______ germ or sex cells;

crossing over and independent assortment of

chromosomes also occur, resulting in four

genetically variable cells.

______ produces identical _____ somatic cells.

meiosis, haploid, mitosis, diploid

The form of meiosis that produces sperm cells is called ________, which produces _____ mature sperm

spermatogenesis, four

The form of meiosis that produces egg cells is called ________, which produces _____ non-functional polar bodies and only ____ functional egg.

oogenesis, three, one

_____ used a species of pea plant to monitor traits of

parent plants and how they were passed to offspring.

The traits Mendel monitored in the peas included the _______ or physical characteristics of an individual such as color & texture of seeds, pods, color & position of blossoms, and stem length. This is determined by the _______ or the genetic makeup of the individual

mendel, phenotype, genotype

_______ are different forms of a gene located on separate but related ____ of the chromosome. EX: one allele results in brown eye color phenotype and the other results in blue eye color phenotype.

Dominant traits means that only ___ allele is required to produce the phenotype.

alleles, arms

Genotype designations:

YY: _______ ________
Yy: ________ _________

yy: _______ ______

homozygous dominant, heterozygous dominant, homozygous recessive

By cross-fertilizing pea plants and observing the first generation progeny, Mendel would then allow the offspring to self-pollinate. What he found in these so-called F1 and F2 generations was a predictable set of outcomes.

Mendel’s proportional analysis was ground-

breaking. Because of it, we can use a tool called a

________ ______ to predict ratios of genotypes and

phenotypes in offspring.

punnet square

In this example, there is a 50% probability that the offspring will be heterozygous dominant and a 50% probability it will be homozygous recessive for the trait.

Such a prediction (analyzing one trait at a time) is called a _______ ______

monohybrid cross

This is an example of two traits in a punnet square, called a _______ _____.

dihybrid cross

Other means of inheritance:
_______ Dominance
There are situations where neither allele is
dominant, but both are incompletely dominant.
The classic example of incomplete dominance is the
crossing of red snapdragons with white snapdragons
to produce pink offspring. RR (red) + rr (white) = Rr (pink). This is due to there being less red pigment than there normally would be.

incomplete

Other means of inheritance:
___________

In this situation, both alleles are expressed ______.

The classic example is blood typing. Blood types refer

to certain proteins found on the surface of red blood

cells. Alleles can code for proteins A or B.

It is possible for both

alleles to be inactive and code for

neither protein. This is the O blood

type

codominance, equally

______ inheritance or multiple alleles EX: Skin color and height

One trait is affected by two or more sets of alleles.

Genotypes & Phenotypes:

AABB Very dark skin

AABb or AaBB Dark

AaBb or Aabb or aaBB Medium brown

Aabb or aaBb Light

Aabb Very light

Example: skin color

polygenic

______ - one gene can have many effects

In Mendel's pea plants, seed coat color was
always associated with specific flower and axil colors.

pleiotropy

______ Laws:

Law of ______- Alleles separate ________ the

formation of gametes, or egg and sperm (this is what

we now perceive as homologous chromosomes that

separate during meiosis).

Law of ________ Assortment - individual traits are

transmitted _______ being affected by others (what

we now know as the random alignment of chromosomes

during Metaphase I of meiosis).

segregation, before, independent, without

proteins are composed of ____ _____ linked together by ______ bonds.

protein production takes place in 2 main areas: the ______ and on _______ (either on the ER or the cytoplasm)

proteins amino acids, peptide, nucleus, ribosomes