cell division meiosis Flashcards
Type of cell division in sexually reproducing organisms that reduces the number of chromosomes in gametes.
MEIOSIS
DIPLOID (2N) - A CELL WITH TWO OF EACH KIND OF CHROMOSOME.
ONE CHROMOSOME FROM EACH PARENT.
IF TWO BODY CELLS WERE TO COMBINE NUCLEI, THE NUMBER OF CHROMOSOMES WOULD DOUBLE.
IN ORDER FOR SEXUAL REPRODUCTION TO OCCUR, EACH CELL INVOLVED MUST REDUCE ITS CHROMOSOME NUMBER BY HALF.
HAPLOID (N)- A CELL WITH ONE OF EACH KIND OF CHROMOSOME
Meiosis
ARE PAIRED CHROMOSOMES WITH GENES FOR THE SAME TRAIT ARRANGED IN THE SAME ORDER.
EX. EYE COLOR, HAIR COLOR, HEIGHT, ONE MAY CODE FOR BLUE, BLONDE, TALL, ITS HOMOLOG MAY CODE FOR BROWN, BLONDE, SHORT
HOMOLOGOUS CHROMOSOMES MAY HAVE DIFFERENT ALLELES ON THEM
ALLELE- GENE FORM FOR EACH VARIATION OF A TRAIT OF AN ORGANISM.
HOMOLOGOUS CHROMOSOMES
IS THE PROCESS OF CELL DIVISION IN WHICH GAMETES ARE FORMED AND THE NUMBER OF CHROMOSOMES IS HALVED. SO THAT SEXUAL REPRODUCTION AND ZYGOTE FORMATION CAN OCCUR.
ZYGOTE- FERTILIZED EGG WHICH HAS A DIPLOID NUMBER OF CHROMOSOMES.
Meiosis
FERTILIZED EGG WHICH HAS A DIPLOID NUMBER OF CHROMOSOMES.
Zygote
INTERPHASE-
CHROMOSOMES REPLICATE
EACH CHROMOSOME CONSISTS OF 2 IDENTICAL SISTER CHROMATIDS
PROPHASE I
EACH PAIR OF HOMOLOGOUS CHROMOSOMES COME TOGETHER TO FORM A TETRAD.
TETRAD- 2 HOMOLOGOUS CHROMOSOMES COME TOGETHER AND THE 4 CHROMATIDS OVERLAP.
STAGES OF MEIOSIS
TETRADS ARE SO TIGHT THAT NON-SISTER CHROMATIDS FROM THE HOMOLOGOUS PAIR ACTUALLY EXCHANGE GENETIC MATERIAL.
CROSSING OVER- THE EXCHANGE OF GENETIC MATERIAL BY NON-SISTER CHROMATIDS DURING LATE PROPHASE I OF MEIOSIS.
RESULTS IN A NEW COMBINATION OF ALLELES
crossing over
HOMOLOGOUS CHROMOSOMES LINE UP TOGETHER IN PAIRS.
IN MITOSIS HOMOLOGOUS CHROMOSOMES LINE UP IN THE MIDDLE INDEPENDENTLY OF EACH OTHER.
Metaphase 1
SPINDLE FIBERS ATTACH TO THE CENTROMERES OF EACH PAIR.
HOMOLOGOUS CHROMOSOMES SEPARATE AND MOVE TO OPPOSITE ENDS OF THE CELL.
CENTROMERES DO NOT SPLIT LIKE THEY DO IN MITOSIS
NOW EACH CELL WILL GET ONE CHROMOSOME FROM EACH HOMOLOGOUS PAIR.
Anaphase 1
SPINDLE FIBERS BREAK DOWN
CHROMOSOMES UNCOIL
CYTOPLASM DIVIDES
ANOTHER CELL DIVISION IS NEEDED BECAUSE THE NUMBER OF CHROMOSOMES HAS NOT BEEN REDUCED
AFTER TELOPHASE I THERE MAYBE A SHORT INTERPHASE, BUT NOT ALWAYS. IT IS IMPORTANT TO NOTE THAT IF A CELL DOES HAVE A SECOND INTERPHASE, THERE IS NO REPLICATION OF CHROMOSOMES.
Telophase 1
IS BASICALLY JUST LIKE MITOSIS, BUT REMEMBER THE CHROMOSOMES DID NOT DUPLICATE IN INTERPHASE II.
PROPHASE II
CHROMOSOMES BEGIN TO LINE UP IN THE MIDDLE OF THE CELL.
SPINDLE FIBERS BEGIN TO FORM
METAPHASE II
CHROMOSOMES LINE UP ON THE METAPHASE PLATE
meiosis II
ANAPHASE II
CENTROMERES SPLIT
SISTER CHROMATIDS SEPARATE AND MOVE TO OPPOSITE SIDES OF THE CELL
TELOPHASE II
NUCLEI REFORM
SPINDLE FIBERS DISAPPEAR
CYTOPLASM DIVIDES INTO TWO.
THE NUMBER OF CHROMOSOMES IN EACH DAUGHTER CELL HAS NOW BEEN REDUCED BY HALF.
MeiosisII
IS A FIELD OF BIOLOGY THAT STUDIES HOW TRAITS ARE PASSED FROM PARENTS TO THEIR OFFSPRING. THE PASSING OF TRAITS FROM PARENTS TO OFFSPRING IS KNOWN AS HEREDITY, THEREFORE, GENETICS IS THE STUDY OF HEREDITY.
genetics
is the cornerstone of genetics and is the perfect place to start for an introduction to genetics. DNA stands for deoxyribonucleic acid and it is the molecule that holds the genetic information for a cell and an organism.
DNA - introduction to geneticsA DNA molecule contains a code that can be used by a cell to express certain genes. Specific sections of a DNA molecule provides the information to build specific proteins which can then be used by a cell to express the desired gene.
DNA
- introduction to geneticsA DNA molecule contains a code that can be used by a cell to express certain genes. Specific sections of a DNA molecule provides the information to build specific proteins which can then be used by a cell to express the desired gene.
DNA
IS A SPECIFIC SEGMENT OF A DNA MOLECULE THAT HOLDS THE INFORMATION FOR ONE SPECIFIC PROTEIN. DNA MOLECULES HAVE A UNIQUE CODE FOR EACH GENE WHICH CODES FOR THEIR SPECIFIC PROTEIN. SOME ORGANISMS CAN HAVE MORE THAN 100,000 DIFFERENT GENES SO THEY WILL HAVE 100,000 UNIQUE SEQUENCES OF DNA ‘CODE’.
GENES ARE THE BASIC UNIT OF HEREDITY. THE GENES OF AN INDIVIDUAL ARE DETERMINED BY THEIR PARENT OR PARENTS. A BACTERIA THAT IS BORN BY ONE PARENT CELL SPLITTING INTO TWO CELLS AND HAS THE EXACT SAME GENES AS THEIR ONE PARENT CELL.
genes
is the backbone of genetics and is an important topic to cover in an introduction to genetics. Long before DNA had been discovered and the word ‘genetics’ had been invented, people were studying the inheritance of traits from one generation to the nex
GENETICS AND INHERITANCE
Genetic inheritance occurs both in sexual reproduction and asexual reproduction. In sexual reproduction, two organisms contribute DNA to produce a new organism. In asexual reproduction, one organism provides all the DNA and produces a clone of themselves. In either, genetic material is passed from one generation to the next.
genetic and inheritance
A CELL WITH TWO OF EACH KIND OF CHROMOSOME.
DIPLOID (2N)
A CELL WITH ONE OF EACH KIND OF CHROMOSOME.
HAPLOID (N)
GENE FORM FOR EACH VARIATION OF A TRAIT OF AN ORGANISM.
Allele
FERTILIZED EGG WHICH HAS A DIPLOID NUMBER OF CHROMOSOMES.
zygote
