Chapter 4 Flashcards
Define heredity
The passing of traits from parents to offspring
Define genetics
The scientific study of heredity and variation
What is DNA’s full name?
Deoxyribonucleic acid
Define deoxyribonucleic acid
A molecule that carries genetic information for cells (makes up a chromosome)
Define gene
A segment of DNA that codes for a particular trait
Define locus
Location of a gene on a chromosome
Define chromosomes
They are found in the nucleus of eukaryotic cells. They vary in shape, size and number between species but usually remain consistent within species.
How many chromosomes does a human have?
46 (23 pairs)
What is 2N ?
Short form for diploid cell
What is N ?
Short form for haploid cells
What is a haploid cell?
They have half the normal number of chromosomes
What is a polyploid cell?
It has three or more sets of chromosomes
What is the cell cycle?
It refers to the sequence of events from one division to another. It includes interphase mitosis and cytokinesis.
Define Interphase
The phase that takes up most of the cells life. It gathers nutrients and grows in this stage. The genetic material must be duplicated for cell division. At the end of interphase, double sets of chromosomes exist and are referred to as sister chromatids.
What is chromatin?
The genetic material which is made up of DNA strands. Chromosomes in this form are long and thin.
Define mitosis
The process that ensures that each new cell has a nucleus with chromatin. It is made up of four stages.
What is prophase?
The stage at which chromosomes become short and fat. The nuclear membrane starts to dissolve. The centrioles migrate to the poles of the cell and form spindle fibres which will attach to the centromere.
What is metaphase?
The stage when chromosomes line up at the center of the cell.
What is anaphase?
The stage when the centromere divides and the spindle fibers move and align. The sister chromatids separate and are pulled to opposite poles in the cell
What is telophase?
The stage when a complete set of chromosomes are at each pool of the cell. Single-stranded chromosomes unwind into thin strands of chromatin and spindle fibers dissolve. The nuclear membrane reforms
What is cytokinesis?
The stage at which the cytoplasm and organelles separate so two new cells are formed. In many protists, fungi and animals cells, the cell pinches off into two parts. In plant cells, the cell plate forms which separates the cell into two parts.
What is sexual reproduction?
A process that produces genetic variety. The offspring inherit genetic information from both parents, thus differing genetically from everyone else.
How many processes are there in sexual reproduction?
Two. Gamete Formation and Fertilization.
What is gamete formation?
Gametes are haploid sex cells, including sperm and egg cells. Produced by meiosis.
What is fertilization?
The joining together or fusion of two gametes. The new cell produce is called a zygote (a diploid cell). The offspring receive a complete set of genetic information from both parents. Each chromosome from one parent is matched by the other parent.
Define homologous chromosomes
They are matching pairs of chromosomes that are similar in size and carry information for the same genes.
How many copies of chromosomes are normally found in the cells of a diploid organism?
2
In mitosis, replication occurs during….
Interphase
The process by which the cells cytoplasm and its contents are divided into two is called…
Cytokinesis
The non-dividing stage of the cell cycle is called…
Interphase
What encompasses the stages prophase metaphase anaphase and telophase?
Mitosis
What is the name of the structure that joins two sister chromatids together?
Centromere
Describe Meiosis
It is a two-stage cell division in which the resulting daughter cells have half the number of chromosomes as the parent cells. It involves two divisions that produce for haploid cells.
Describe Meiosis I
It is called a reduction division as the diploid chromosome number is reduced by half to the haploid chromosome number.
Defined meiosis II
The chromosome number is unchanged but the total number of sales increases to four.
Why is meiosis important?
Meiosis allows for genetic variation in a population. This is achieved through crossing over where homologous pairs exchange segments of DNA
Describe prophase I
The chromosomes become short and thick and the nuclear membrane dissolves. The sister chromatids find the homologous pairs and form a tetrad. Then synapsis occurs where sister chromatids intertwine with each other and the exchange of DNA occurs during crossing over.
Define metaphase I
The tetrads lineup in the center of the cell.
Define Anaphase I
Homologous chromosomes are pulled to opposite ends by spindle fibers. This is called reaction division because only one sister chromatid from each homologous pair is found in the daughter cell.
Define telophase I
The nuclear membrane reappears and the cell begins to divide. The cells are now haploid
Define prophase II
The nuclear membrane dissolves and spend the fibers form once again.
Define metaphase II
Sister chromatids lineup next to each other along the equator of the cell
Define anaphase II
The sister chromatids separate to the poles. The nuclear membrane reforms and chromatids are now called chromosomes.
Define telophase II/cytokinesis
The cytoplasm divides and four daughter cells are produced. They are all haploid
What is a karyotype?
When the chromosomes of an individual have been sorted and arranged according to size and type. Karyotypes are used to find a gender or genetic problems.
Define gametogenesis.
The production of gametes and animals which occurs in the gonads (reproductive organs).
What is spermatogenesis?
The production of sperm cells in which the cytoplasm is divided evenly, creating 4 smaller sperm cells.
What is oogenesis?
The production of egg cells in which The cytoplasm does not divide equally during meiosis, producing a single ovum and three polar bodies that die.
Define random assortment
During metaphase I, chromosomes are arranged in homologous pairs across the equator of the cell in a random order, causing many different combinations to be found in gametes.
How do you find the number of genetically distinct gametes produced in a diploid organism?
Use 2 to the power of n.
How many genetically distinct gametes can humans (with 23 pairs of chromosomes) produce?
2 to the power of 23 = 8 388 608
What is beneficial to both random assortment and crossing over?
Provides for the great genetic diversity amongst individuals
Define chromosomal abnormalities
Some gametes are produced with chromosome abnormalities in which most don’t survive but some do. There are two types of chromosomal errors. Changes and chromosomal structure and changes in chromosomal number
Describe changes in chromosomal structure
During crossing over, the chemical bonds that hold DNA together are broken and reformed. Sometimes, they do not reform correctly and other times non-homologous pairs may cross over producing chromosomes that contain genes not normally found on the chromosome.
What are the four types of errors in chromosomal structure?
Deletion, duplication, inversion, translocation
Define deletion
A segment of DNA is deleted or gone missing
Define duplication
Extra piece of DNA is added
Define inversion
DNA segment is flipped
DefineTranslocation
A DNA segment from one chromosome gets exchanged with another nonhomologous chromosome
Define changes in chromosomal number
Sometimes homologous pairs or sister chromatids do not separate properly which is referred to as nondisjunction. This can occur in anaphase I or II.
Define monosomy
Monosomy means missing one chromosome. This occurs when there is a single chromosome in place of a homologous pair. For example, in Turner syndrome, there is one X chromosome missing
Define trisomy
Trisomy is when there’s an extra chromosome. It occurs when there are three chromosomes in place of one homologous pair. For example in down syndrome there is an extra 21st chromosome.
Define down syndrome
Called trisomy 21
- flattened facial profile and nose
- short neck with excess skin at back
- small headache ears and mouth with upward slanting eyes
Define Patau Syndrome
Called trisomy 13, extra 13th chromosome
- causes complex defects in multiple organs especially the heart - cleft palate - overlapping fingers over thumb
Define Edwards syndrome.
Called trisomy 18, extra 18th chromosome
- structural heart defects - developmental delays - growth deficiency
Define Klinefelter syndrome
Has an extra copy of the X chromosome (XXY)
- severe speech problem - intellectual disability - less testosterone
Define Turner syndrome
Has missing pieces of or is missing the full second X-chromosome in a girl
- heart abnormalities - brittle bones - learning disabilities
Define cloning
The process of making an organism that is genetically identical by nonsexual means.
- plants can be made faster while taking up less space, grown year round - mass-produced organism with desired qualities - Dolly the sheep was the first cloned animal
Define In Vitro fertilization
A process where an egg is fertilized by sperm outside the body
- used in cattle or other large animals to increased reproduction speed - help large numbers of animals breed while improving gene pool
Define recombinant DNA
rDNA is created by combining two or more different strands of DNA to form artificial DNA
- rDNA is used to improve crops - creates crops that are resistant to insects and herbicides
Define artificial insemination
The introduction of sperm into a female’s uterus or cervix using an artificial insemination device
-used for many different types of animal breeding
What is a diploid cell?
It has two sets of chromosomes
